How to compare time string with current time in java?

How to compare time string with current time in java? - java

I have a time string like "15:30" i want to compare that string with the current time.
Please suggest something easy.
And how to get the current time in hour minute format("HH:mm")

tl;dr
LocalTime
.now()
.isAfter(
LocalTime.parse( "15:30" )
)
Details
You should be thinking the other way around: How to get that string turned into a time value. You would not attempt math by turning your numbers into strings. So too with date-time values.
Avoid the old bundled classes, java.util.Date and .Calendar as they are notoriously troublesome, flawed both in design and implementation. They are supplanted by the new java.time package in Java 8. And java.time was inspired by Joda-Time.
Both java.time and Joda-Time offer a class to capture a time-of-day without any date to time zone: LocalTime.
java.time
Using the java.time classes built into Java, specifically LocalTime. Get the current time-of-day in your local time zone. Construct a time-of-day per your input string. Compare with the isBefore, isAfter, or isEqual methods.
LocalTime now = LocalTime.now();
LocalTime limit = LocalTime.parse( "15:30" );
Boolean isLate = now.isAfter( limit );
Better to specify your desired/expected time zone rather than rely implicitly on the JVM’s current default time zone.
ZoneId z = ZoneId.of( "Pacific/Auckland" ) ;
LocalTime now = LocalTime.now( z ); // Explicitly specify the desired/expected time zone.
LocalTime limit = LocalTime.parse( "15:30" );
Boolean isLate = now.isAfter( limit );
Joda-Time
The code in this case using the Joda-Time library happens to be nearly the same as the code seen above for java.time.
Beware that the Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Just compare the strings as normal like so:
String currentTime = new SimpleDateFormat("HH:mm").format(new Date());
String timeToCompare = "15:30";
boolean x = currentTime.equals(timeToCompare);
If the times are the same x will be true if they are not x will be false

Following would get the time. You can than use it to compare
String currentTime=new SimpleDateFormat("HH:mm").format(new Date());

I have a similar situation where I need to compare time string like "15:30" with the current time.
I am using Java 7 so I can not use Basil Bourque's solution.
So I have implemented one method which takes one string like "15:30" and
check with current time and returns true if current time is after input time.
public static boolean checkSlaMissedOrNot(String sla) throws ParseException {
boolean slaMissedOrnot = false;
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, Integer.parseInt(sla.substring(0, 2)));
cal.set(Calendar.MINUTE, Integer.parseInt(sla.substring(3)));
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
if (Calendar.getInstance().after(cal)) {
System.out.println("it's SLA missed");
slaMissedOrnot = true;
} else {
System.out.println("it's fine & not SLA missed");
}
return slaMissedOrnot;
}
Calendar has other use full methods like after(Object when)
Returns whether this Calendar represents a time after the time represented by the specified Object.
You can use this method also to compare time string with the current time.

So my Solution is a little bit different, Its starts with creating an clock with the current time, and testing the hour agaisnt a user defined int.
public void TextClockWindow() {
this.pack();
javax.swing.Timer t = new javax.swing.Timer(1000, (ActionEvent e) -> {
Calendar calendar = new GregorianCalendar();
String am_pm;
calendar.setTimeZone(TimeZone.getDefault());
Calendar now = Calendar.getInstance();
int h = now.get(Calendar.HOUR_OF_DAY);
int m = now.get(Calendar.MINUTE);
int s = now.get(Calendar.SECOND);
if (calendar.get(Calendar.AM_PM) == 0) {
am_pm = "AM";
} else {
am_pm = "PM";
} // Code to Determine whether the time is AM or PM
Clock.setText("" + h + ":" + m + " " + am_pm);
if(h < 5) { //int here which tests agaisnt the hour evwery second
System.out.println("Success");
} else {
System.out.println("Failure");
}
});
t.start();
}

Try this
public static String compareTime(String d) {
if (null == d)
return "";
try {
SimpleDateFormat sdf= new SimpleDateFormat("HH:mm");
d = sdf.format(new Date());
} catch (Exception e) {
e.printStackTrace();
}
return d;
}
then you can compare with your string

Here is my example to compare before and after current time :
MainActivity.java
Button search = (Button) findViewById(R.id.searchBus);
SimpleDateFormat sdfDate = new SimpleDateFormat("HH:mm");
String limit = "23:00";
Date limitBus=null;
try {
limitBus = sdfDate.parse(limit);
} catch (ParseException e) {
e.printStackTrace();
}
String start = "07:15";
Date startBus=null;
try {
startBus = sdfDate.parse(start);
} catch (ParseException e) {
e.printStackTrace();
}
String user_time = getCurrentTimeStamp();
Date now = null;
try {
now = sdfDate.parse(user_time);
} catch (ParseException e) {
e.printStackTrace();
}
if (now.after(limitBus)||now.before(startBus)){
Toast.makeText(this, "Bus Operation Hours : 7:15AM - 11.00PM", Toast.LENGTH_LONG).show();
search.setEnabled(false);
}
else
{
search.setEnabled(true);
}
//get current time method
public static String getCurrentTimeStamp() {
SimpleDateFormat sdfDate = new SimpleDateFormat("HH:mm");//dd/MM/yyyy
Date now = new Date();
String strDate = sdfDate.format(now);
return strDate;
}

This code will check User Inputted time with current system time and will return time difference in long value.
public long getTimeDifferenceInMillis (String dateTime) {
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long currentTime = new Date().getTime();
long endTime = 0;
try {
//Parsing the user Inputed time ("yyyy-MM-dd HH:mm:ss")
endTime = dateFormat.parse(dateTime).getTime();
} catch (ParseException e) {
e.printStackTrace();
return 0;
}
if (endTime > currentTime)
return endTime - currentTime;
else
return 0;
}
The user should pass the time in "yyyy-MM-dd HH:mm:ss" format.

Related

Date difference in different timezones in java

I am pragmatically building a nested JSON from a table. Json looks something like this:
{"date":"03-16-2018 06:57:02",
"details":
[
{
"motorstate":0,
"startTime":"03-16-2018 20:41:57",
},
{
"motorstate":0,
"startTime":"03-16-2018 06:57:02",
}
]
},
{"date":"03-15-2018 08:08:48",
"details":
[
{
"motorstate":0,
"startTime":"03-16-2018 03:53:30",
}
]
}
If you look into the above example, the second record:
{"date":"03-15-2018 08:08:48",
"details":
[
{
"motorstate":0,
"startTime":"03-16-2018 03:53:30",
}
]
}
The dates are mismatching. This is because the date shown here is in IST but actually stored in UTC in my Google Datastore. In UTC, its still 03-15-2018 and not 03-16-2018.
My question is how can we perform a date difference in different timezones other than UTC in Java? The Date.getTime() method always give the difference in UTC and not in local Timezone.

tl;dr
Date difference in different timezones in java
Period.between(
LocalDateTime.parse(
"03-15-2018 08:08:48" ,
DateTimeFormatter.ofPattern( “MM-dd-uuuu HH:mm:ss” )
)
.atZone( ZoneId.of( ”Asia/Kolkata" ) )
.toLocalDate()
,
LocalDate.now( ZoneId.of( ”Asia/Kolkata" ) )
)
Details
The modern approach uses the java.time classes rather than the troublesome old me old legacy date-time classes such as Date and Calendar.
Tip: Avoid custom formatting patterns when serializing date-time values to text. Use standard ISO 8601 formats only.
Tip: when exchanging date-time values as text, always include an indicator of the offset-from-UTC and the time zone name.
First, parse your input strings as LocalDateTime because they lack any indication of offset or zone.
Define a formatting pattern to match input.
DateTimeFormatter f = DateTimeFormatter.ofPattern( “MM-dd-uuuu HH:mm:ss” ) ;
Parse.
String input = "03-15-2018 08:08:48" ;
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;
You claim to know that these inputs were intended to represent a moment in India time. Apply a ZoneId to get a ZonedDateTime.
ZoneId z = ZoneId.of( ”Asia/Kolkata" ) ;
ZonedDateTime zdt = ldt.atZone( z ) ;
To get the date-only value, extract a LocalDate.
LocalDate ld = zdt.toLocalDate() ;
To represent the delta between dates as a number of years, months, and days unattached to the timeline, use Period.
Period p = Period.between( ldt , LocalDate.now( z ) ) ;
For a count of total days.
long days = ChronoUnit.DAYS.between( start , stop ) ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

public String getSummary(String deviceGuid)
{
Query<com.google.cloud.datastore.Entity> query
= Query.newEntityQueryBuilder()
.setKind("sensordata")
.setFilter(PropertyFilter.eq("deviceguid", deviceGuid))
.setOrderBy(OrderBy.desc("startTime"))
.build();
QueryResults<com.google.cloud.datastore.Entity> resultList =
datastore.run(query);
if(!resultList.hasNext())
{
log.warning("No record found..");
return "No record found";
}
com.google.cloud.datastore.Entity e =null;
com.google.cloud.datastore.Entity pe =null;
SensorDataOut sensorDataOut = new SensorDataOut();
SensorSummaryDataOut summary = new SensorSummaryDataOut();
TotalSummaryDataOut totalSummary = new TotalSummaryDataOut();
Calendar calendar = Calendar.getInstance();
calendar.setTimeZone(TimeZone.getTimeZone("IST"));
Calendar calendar1 = Calendar.getInstance();
calendar1.setTimeZone(TimeZone.getTimeZone("IST"));
SimpleDateFormat sdf = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
sdf.setTimeZone(TimeZone.getTimeZone("IST"));
SimpleDateFormat sdf1 = new SimpleDateFormat("MM-dd-yyyy");
//sdf.setTimeZone(TimeZone.getTimeZone("IST"));
long stopTime;
long startTime;
long pStartTime;
long diffTime;
long diffDay;
Date pDateWithoutTime;
Date eDateWithoutTime;
while(resultList.hasNext())
{
e = resultList.next();
startTime = (e.contains("startTime"))?e.getTimestamp("startTime").toSqlTimestamp().getTime():0;
stopTime = (e.contains("stopTime"))?e.getTimestamp("stopTime").toSqlTimestamp().getTime():0;
//log.info("Start Date : " + e.getTimestamp("startTime").toString() + " - " + String.valueOf(startTime));
//log.info("Stop Date : " + e.getTimestamp("stopTime").toString() + " - " + String.valueOf(stopTime));
//log.info("Usage Volume :" + String.valueOf(e.getLong("usageVolume")));
sensorDataOut = new SensorDataOut();
calendar.setTimeInMillis(stopTime);
sensorDataOut.stopTime = sdf.format(calendar.getTime());
calendar.setTimeInMillis(startTime);
sensorDataOut.startTime = sdf.format(calendar.getTime());
sensorDataOut.motorstate = (e.contains("motorstate"))?(int)e.getLong("motorstate"):-1;
sensorDataOut.startVolume = (e.contains("startVolume"))?(int)e.getLong("startVolume"):-1;
sensorDataOut.stopVolume = (e.contains("stopVolume"))?(int)e.getLong("stopVolume"):-1;
sensorDataOut.usageTime = (e.contains("usageTime"))?e.getLong("usageTime"):-1;
sensorDataOut.usageVolume = (e.contains("usageVolume"))?(int)e.getLong("usageVolume"):-1;
if(pe!=null)
{
//Get the date difference in terms of days. If it is same day then add the volume consumed
pStartTime= pe.getTimestamp("startTime").toSqlTimestamp().getTime();
try{
calendar.setTimeInMillis(pStartTime);
pDateWithoutTime = sdf1.parse(sdf1.format(calendar.getTime()));
calendar1.setTimeInMillis(e.getTimestamp("startTime").toSqlTimestamp().getTime());
eDateWithoutTime = sdf1.parse(sdf1.format(calendar1.getTime()));
}
catch(Exception ex){
log.info("Exception while parsing date");
continue;
}
diffTime = Math.abs(pDateWithoutTime.getTime() - eDateWithoutTime.getTime());
diffDay = TimeUnit.DAYS.convert(diffTime, TimeUnit.MILLISECONDS);
//log.info("pDateWithoutTime: " + pDateWithoutTime + ", eDateWithoutTime: " + eDateWithoutTime + ", consumedVolume: "
// + sensorDataOut.usageVolume;
if(diffDay!=0) //If not same day
{
totalSummary.totVolume = totalSummary.totVolume + summary.totVolume;
totalSummary.totDuration = totalSummary.totDuration + summary.totDuration;
totalSummary.details.add(summary);
summary = new SensorSummaryDataOut();
}
}
summary.date = sensorDataOut.startTime;
summary.totVolume = summary.totVolume + sensorDataOut.usageVolume;
summary.totDuration = summary.totDuration + sensorDataOut.usageTime;
summary.details.add(sensorDataOut);
pe = e;
}
if(summary.details.size()>0)
{
totalSummary.totVolume = totalSummary.totVolume + summary.totVolume;
totalSummary.totDuration = totalSummary.totDuration + summary.totDuration;
totalSummary.details.add(summary);
summary = new SensorSummaryDataOut();
}
totalSummary.avgVolume = totalSummary.totVolume/totalSummary.details.size();
totalSummary.deviceguid = deviceGuid;
String json = "";
Gson gson = new Gson();
json = gson.toJson(totalSummary);
return json;
} //End of Function

Below method will return you your UTC time to current Timezone and this worked for me
public static Date getLocalDateObjFromUTC(String date, String time) throws ParseException {
String dateAndTimeInUTC = date + " " + time;
SimpleDateFormat localDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
localDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
Date dateInLocalTimeZone = localDateFormat.parse(dateAndTimeInUTC);
return dateInLocalTimeZone;
}

Getting wrong date '01:00:00' when using SimpleDateFormat.parse() [duplicate]

Want to improve this post? Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.
When I create a new Date object, it is initialized to the current time but in the local timezone. How can I get the current date and time in GMT?

tl;dr
Instant.now() // Capture the current moment in UTC.
Generate a String to represent that value:
Instant.now().toString()
2016-09-13T23:30:52.123Z
Details
As the correct answer by Jon Skeet stated, a java.util.Date object has no time zone†. But its toString implementation applies the JVM’s default time zone when generating the String representation of that date-time value. Confusingly to the naïve programmer, a Date seems to have a time zone but does not.
The java.util.Date, j.u.Calendar, and java.text.SimpleDateFormat classes bundled with Java are notoriously troublesome. Avoid them. Instead, use either of these competent date-time libraries:
java.time.* package in Java 8
Joda-Time
java.time (Java 8)
Java 8 brings an excellent new java.time.* package to supplant the old java.util.Date/Calendar classes.
Getting current time in UTC/GMT is a simple one-liner…
Instant instant = Instant.now();
That Instant class is the basic building block in java.time, representing a moment on the timeline in UTC with a resolution of nanoseconds.
In Java 8, the current moment is captured with only up to milliseconds resolution. Java 9 brings a fresh implementation of Clock captures the current moment in up to the full nanosecond capability of this class, depending on the ability of your host computer’s clock hardware.
It’s toString method generates a String representation of its value using one specific ISO 8601 format. That format outputs zero, three, six or nine digits digits (milliseconds, microseconds, or nanoseconds) as necessary to represent the fraction-of-second.
If you want more flexible formatting, or other additional features, then apply an offset-from-UTC of zero, for UTC itself (ZoneOffset.UTC constant) to get a OffsetDateTime.
OffsetDateTime now = OffsetDateTime.now( ZoneOffset.UTC );
Dump to console…
System.out.println( "now.toString(): " + now );
When run…
now.toString(): 2014-01-21T23:42:03.522Z
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
Joda-Time
UPDATE: The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
Using the Joda-Time 3rd-party open-source free-of-cost library, you can get the current date-time in just one line of code.
Joda-Time inspired the new java.time.* classes in Java 8, but has a different architecture. You may use Joda-Time in older versions of Java. Joda-Time continues to work in Java 8 and continues to be actively maintained (as of 2014). However, the Joda-Time team does advise migration to java.time.
System.out.println( "UTC/GMT date-time in ISO 8601 format: " + new org.joda.time.DateTime( org.joda.time.DateTimeZone.UTC ) );
More detailed example code (Joda-Time 2.3)…
org.joda.time.DateTime now = new org.joda.time.DateTime(); // Default time zone.
org.joda.time.DateTime zulu = now.toDateTime( org.joda.time.DateTimeZone.UTC );
Dump to console…
System.out.println( "Local time in ISO 8601 format: " + now );
System.out.println( "Same moment in UTC (Zulu): " + zulu );
When run…
Local time in ISO 8601 format: 2014-01-21T15:34:29.933-08:00
Same moment in UTC (Zulu): 2014-01-21T23:34:29.933Z
For more example code doing time zone work, see my answer to a similar question.
Time Zone
I recommend you always specify a time zone rather than relying implicitly on the JVM’s current default time zone (which can change at any moment!). Such reliance seems to be a common cause of confusion and bugs in date-time work.
When calling now() pass the desired/expected time zone to be assigned. Use the DateTimeZone class.
DateTimeZone zoneMontréal = DateTimeZone.forID( "America/Montreal" );
DateTime now = DateTime.now( zoneMontréal );
That class holds a constant for UTC time zone.
DateTime now = DateTime.now( DateTimeZone.UTC );
If you truly want to use the JVM’s current default time zone, make an explicit call so your code is self-documenting.
DateTimeZone zoneDefault = DateTimeZone.getDefault();
ISO 8601
Read about ISO 8601 formats. Both java.time and Joda-Time use that standard’s sensible formats as their defaults for both parsing and generating strings.
† Actually, java.util.Date does have a time zone, buried deep under layers of source code. For most practical purposes, that time zone is ignored. So, as shorthand, we say java.util.Date has no time zone. Furthermore, that buried time zone is not the one used by Date’s toString method; that method uses the JVM’s current default time zone. All the more reason to avoid this confusing class and stick with Joda-Time and java.time.

java.util.Date has no specific time zone, although its value is most commonly thought of in relation to UTC. What makes you think it's in local time?
To be precise: the value within a java.util.Date is the number of milliseconds since the Unix epoch, which occurred at midnight January 1st 1970, UTC. The same epoch could also be described in other time zones, but the traditional description is in terms of UTC. As it's a number of milliseconds since a fixed epoch, the value within java.util.Date is the same around the world at any particular instant, regardless of local time zone.
I suspect the problem is that you're displaying it via an instance of Calendar which uses the local timezone, or possibly using Date.toString() which also uses the local timezone, or a SimpleDateFormat instance, which, by default, also uses local timezone.
If this isn't the problem, please post some sample code.
I would, however, recommend that you use Joda-Time anyway, which offers a much clearer API.

SimpleDateFormat dateFormatGmt = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ss");
dateFormatGmt.setTimeZone(TimeZone.getTimeZone("GMT"));
//Local time zone
SimpleDateFormat dateFormatLocal = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ss");
//Time in GMT
return dateFormatLocal.parse( dateFormatGmt.format(new Date()) );

This definitely returns UTC time: as String and Date objects !
static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
public static Date getUTCdatetimeAsDate() {
// note: doesn't check for null
return stringDateToDate(getUTCdatetimeAsString());
}
public static String getUTCdatetimeAsString() {
final SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
final String utcTime = sdf.format(new Date());
return utcTime;
}
public static Date stringDateToDate(String StrDate) {
Date dateToReturn = null;
SimpleDateFormat dateFormat = new SimpleDateFormat(DATEFORMAT);
try {
dateToReturn = (Date)dateFormat.parse(StrDate);
}
catch (ParseException e) {
e.printStackTrace();
}
return dateToReturn;
}

Calendar c = Calendar.getInstance();
System.out.println("current: "+c.getTime());
TimeZone z = c.getTimeZone();
int offset = z.getRawOffset();
if(z.inDaylightTime(new Date())){
offset = offset + z.getDSTSavings();
}
int offsetHrs = offset / 1000 / 60 / 60;
int offsetMins = offset / 1000 / 60 % 60;
System.out.println("offset: " + offsetHrs);
System.out.println("offset: " + offsetMins);
c.add(Calendar.HOUR_OF_DAY, (-offsetHrs));
c.add(Calendar.MINUTE, (-offsetMins));
System.out.println("GMT Time: "+c.getTime());

Actually not time, but it's representation could be changed.
SimpleDateFormat f = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ss");
f.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(f.format(new Date()));
Time is the same in any point of the Earth, but our perception of time could be different depending on location.

This works for getting UTC milliseconds in Android.
Calendar c = Calendar.getInstance();
int utcOffset = c.get(Calendar.ZONE_OFFSET) + c.get(Calendar.DST_OFFSET);
Long utcMilliseconds = c.getTimeInMillis() + utcOffset;

Calendar aGMTCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
Then all operations performed using the aGMTCalendar object will be done with the GMT time zone and will not have the daylight savings time or fixed offsets applied
Wrong!
Calendar aGMTCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
aGMTCalendar.getTime(); //or getTimeInMillis()
and
Calendar aNotGMTCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT-2"));aNotGMTCalendar.getTime();
will return the same time. Idem for
new Date(); //it's not GMT.

This code prints the current time UTC.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class Test
{
public static void main(final String[] args) throws ParseException
{
final SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss z");
f.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(f.format(new Date()));
}
}
Result
2013-10-26 14:37:48 UTC

Here is what seems to be incorrect in Jon Skeet's answer. He said:
java.util.Date is always in UTC. What makes you think it's in local
time? I suspect the problem is that you're displaying it via an
instance of Calendar which uses the local timezone, or possibly using
Date.toString() which also uses the local timezone.
However, the code:
System.out.println(new java.util.Date().getHours() + " hours");
gives the local hours, not GMT (UTC hours), using no Calendar and no SimpleDateFormat at all.
That is why is seems something is incorrect.
Putting together the responses, the code:
System.out.println(Calendar.getInstance(TimeZone.getTimeZone("GMT"))
.get(Calendar.HOUR_OF_DAY) + " Hours");
shows the GMT hours instead of the local hours -- note that getTime.getHours() is missing because that would create a Date() object, which theoretically stores the date in GMT, but gives back the hours in the local time zone.

If you want a Date object with fields adjusted for UTC you can do it like this with Joda Time:
import org.joda.time.DateTimeZone;
import java.util.Date;
...
Date local = new Date();
System.out.println("Local: " + local);
DateTimeZone zone = DateTimeZone.getDefault();
long utc = zone.convertLocalToUTC(local.getTime(), false);
System.out.println("UTC: " + new Date(utc));

You can use:
Calendar aGMTCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
Then all operations performed using the aGMTCalendar object will be done with the GMT time zone and will not have the daylight savings time or fixed offsets applied. I think the previous poster is correct that the Date() object always returns a GMT it's not until you go to do something with the date object that it gets converted to the local time zone.

SimpleDateFormat dateFormatGmt = new SimpleDateFormat("yyyy-MM-dd");
dateFormatGmt.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(dateFormatGmt.format(date));

Here is my implementation of toUTC:
public static Date toUTC(Date date){
long datems = date.getTime();
long timezoneoffset = TimeZone.getDefault().getOffset(datems);
datems -= timezoneoffset;
return new Date(datems);
}
There's probably several ways to improve it, but it works for me.

You can directly use this
SimpleDateFormat dateFormatGmt = new SimpleDateFormat("dd:MM:yyyy HH:mm:ss");
dateFormatGmt.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(dateFormatGmt.format(new Date())+"");

Here an other suggestion to get a GMT Timestamp object:
import java.sql.Timestamp;
import java.util.Calendar;
...
private static Timestamp getGMT() {
Calendar cal = Calendar.getInstance();
return new Timestamp(cal.getTimeInMillis()
-cal.get(Calendar.ZONE_OFFSET)
-cal.get(Calendar.DST_OFFSET));
}

Here is another way to get GMT time in String format
String DATE_FORMAT = "EEE, dd MMM yyyy HH:mm:ss z" ;
final SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT);
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
String dateTimeString = sdf.format(new Date());

With:
Calendar cal = Calendar.getInstance();
Then cal have the current date and time.
You also could get the current Date and Time for timezone with:
Calendar cal2 = Calendar.getInstance(TimeZone.getTimeZone("GMT-2"));
You could ask cal.get(Calendar.DATE); or other Calendar constant about others details.
Date and Timestamp are deprecated in Java. Calendar class it isn't.

Sample code to render system time in a specific time zone and a specific format.
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
public class TimZoneTest {
public static void main (String[] args){
//<GMT><+/-><hour>:<minutes>
// Any screw up in this format, timezone defaults to GMT QUIETLY. So test your format a few times.
System.out.println(my_time_in("GMT-5:00", "MM/dd/yyyy HH:mm:ss") );
System.out.println(my_time_in("GMT+5:30", "'at' HH:mm a z 'on' MM/dd/yyyy"));
System.out.println("---------------------------------------------");
// Alternate format
System.out.println(my_time_in("America/Los_Angeles", "'at' HH:mm a z 'on' MM/dd/yyyy") );
System.out.println(my_time_in("America/Buenos_Aires", "'at' HH:mm a z 'on' MM/dd/yyyy") );
}
public static String my_time_in(String target_time_zone, String format){
TimeZone tz = TimeZone.getTimeZone(target_time_zone);
Date date = Calendar.getInstance().getTime();
SimpleDateFormat date_format_gmt = new SimpleDateFormat(format);
date_format_gmt.setTimeZone(tz);
return date_format_gmt.format(date);
}
}
Output
10/08/2011 21:07:21
at 07:37 AM GMT+05:30 on 10/09/2011
at 19:07 PM PDT on 10/08/2011
at 23:07 PM ART on 10/08/2011

Just to make this simpler, to create a Date in UTC you can use Calendar :
Calendar.getInstance(TimeZone.getTimeZone("UTC"));
Which will construct a new instance for Calendar using the "UTC" TimeZone.
If you need a Date object from that calendar you could just use getTime().

Converting Current DateTime in UTC:
DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
DateTimeZone dateTimeZone = DateTimeZone.getDefault(); //Default Time Zone
DateTime currDateTime = new DateTime(); //Current DateTime
long utcTime = dateTimeZone.convertLocalToUTC(currDateTime .getMillis(), false);
String currTime = formatter.print(utcTime); //UTC time converted to string from long in format of formatter
currDateTime = formatter.parseDateTime(currTime); //Converted to DateTime in UTC

public static void main(String args[]){
LocalDate date=LocalDate.now();
System.out.println("Current date = "+date);
}

This worked for me, returns the timestamp in GMT!
Date currDate;
SimpleDateFormat dateFormatGmt = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ss");
dateFormatGmt.setTimeZone(TimeZone.getTimeZone("GMT"));
SimpleDateFormat dateFormatLocal = new SimpleDateFormat("yyyy-MMM-dd HH:mm:ss");
long currTime = 0;
try {
currDate = dateFormatLocal.parse( dateFormatGmt.format(new Date()) );
currTime = currDate.getTime();
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

The Simple Function that you can use:
Edit: this version uses the modern java.time classes.
private static final DateTimeFormatter FORMATTER
= DateTimeFormatter.ofPattern("dd-MM-uuuu HH:mm:ss z");
public static String getUtcDateTime() {
return ZonedDateTime.now(ZoneId.of("Etc/UTC")).format(FORMATTER);
}
Return value from the method:
26-03-2022 17:38:55 UTC
Original function:
public String getUTC_DateTime() {
SimpleDateFormat dateTimeFormat = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss z");
dateTimeFormat.setTimeZone(TimeZone.getTimeZone("UTC"));//gmt
return dateTimeFormat.format(new Date());
}
return of above function:
26-03-2022 08:07:21 UTC

To put it simple. A calendar object stores information about time zone but when you perform cal.getTime() then the timezone information will be lost. So for Timezone conversions I will advice to use DateFormat classes...

this is my implementation:
public static String GetCurrentTimeStamp()
{
Calendar cal=Calendar.getInstance();
long offset = cal.getTimeZone().getOffset(System.currentTimeMillis());//if you want in UTC else remove it .
return new java.sql.Timestamp(System.currentTimeMillis()+offset).toString();
}

Use this Class to get ever the right UTC Time from a Online NTP Server:
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
class NTP_UTC_Time
{
private static final String TAG = "SntpClient";
private static final int RECEIVE_TIME_OFFSET = 32;
private static final int TRANSMIT_TIME_OFFSET = 40;
private static final int NTP_PACKET_SIZE = 48;
private static final int NTP_PORT = 123;
private static final int NTP_MODE_CLIENT = 3;
private static final int NTP_VERSION = 3;
// Number of seconds between Jan 1, 1900 and Jan 1, 1970
// 70 years plus 17 leap days
private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L;
private long mNtpTime;
public boolean requestTime(String host, int timeout) {
try {
DatagramSocket socket = new DatagramSocket();
socket.setSoTimeout(timeout);
InetAddress address = InetAddress.getByName(host);
byte[] buffer = new byte[NTP_PACKET_SIZE];
DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT);
buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);
writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET);
socket.send(request);
// read the response
DatagramPacket response = new DatagramPacket(buffer, buffer.length);
socket.receive(response);
socket.close();
mNtpTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
} catch (Exception e) {
// if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
return false;
}
return true;
}
public long getNtpTime() {
return mNtpTime;
}
/**
* Reads an unsigned 32 bit big endian number from the given offset in the buffer.
*/
private long read32(byte[] buffer, int offset) {
byte b0 = buffer[offset];
byte b1 = buffer[offset+1];
byte b2 = buffer[offset+2];
byte b3 = buffer[offset+3];
// convert signed bytes to unsigned values
int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0);
int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1);
int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2);
int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3);
return ((long)i0 << 24) + ((long)i1 << 16) + ((long)i2 << 8) + (long)i3;
}
/**
* Reads the NTP time stamp at the given offset in the buffer and returns
* it as a system time (milliseconds since January 1, 1970).
*/
private long readTimeStamp(byte[] buffer, int offset) {
long seconds = read32(buffer, offset);
long fraction = read32(buffer, offset + 4);
return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L);
}
/**
* Writes 0 as NTP starttime stamp in the buffer. --> Then NTP returns Time OFFSET since 1900
*/
private void writeTimeStamp(byte[] buffer, int offset) {
int ofs = offset++;
for (int i=ofs;i<(ofs+8);i++)
buffer[i] = (byte)(0);
}
}
And use it with:
long now = 0;
NTP_UTC_Time client = new NTP_UTC_Time();
if (client.requestTime("pool.ntp.org", 2000)) {
now = client.getNtpTime();
}
If you need UTC Time "now" as DateTimeString use function:
private String get_UTC_Datetime_from_timestamp(long timeStamp){
try{
Calendar cal = Calendar.getInstance();
TimeZone tz = cal.getTimeZone();
int tzt = tz.getOffset(System.currentTimeMillis());
timeStamp -= tzt;
// DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss",Locale.getDefault());
DateFormat sdf = new SimpleDateFormat();
Date netDate = (new Date(timeStamp));
return sdf.format(netDate);
}
catch(Exception ex){
return "";
}
}
and use it with:
String UTC_DateTime = get_UTC_Datetime_from_timestamp(now);

If you want to avoid parsing the date and just want a timestamp in GMT, you could use:
final Date gmt = new Timestamp(System.currentTimeMillis()
- Calendar.getInstance().getTimeZone()
.getOffset(System.currentTimeMillis()));

public class CurrentUtcDate
{
public static void main(String[] args) {
Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println("UTC Time is: " + dateFormat.format(date));
}
}
Output:
UTC Time is: 22-01-2018 13:14:35
You can change the date format as needed.

Current date in the UTC
Instant.now().toString().replaceAll("T.*", "");

How to compare two dates along with time in java

I have two Date objects with the below format.
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
String matchDateTime = sdf.parse("2014-01-16T10:25:00");
Date matchDateTime = null;
try {
matchDateTime = sdf.parse(newMatchDateTimeString);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// get the current date
Date currenthDateTime = null;
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
Date dt = new Date();
String currentDateTimeString = dateFormat.format(dt);
Log.v("CCCCCurrent DDDate String is:", "" + currentDateTimeString);
try {
currenthDateTime = sdf.parse(currentDateTimeString);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Now I want to compare the above two dates along with time.
How should I compare in Java.
Thanks

Since Date implements Comparable<Date>, it is as easy as:
date1.compareTo(date2);
As the Comparable contract stipulates, it will return a negative integer/zero/positive integer if date1 is considered less than/the same as/greater than date2 respectively (ie, before/same/after in this case).
Note that Date has also .after() and .before() methods which will return booleans instead.

An Alternative is....
Convert both dates into milliseconds as below
Date d = new Date();
long l = d.getTime();
Now compare both long values

Use compareTo()
Return Values
0 if the argument Date is equal to this Date; a value less than 0 if this Date is before the Date argument; and a value greater than 0 if this Date is after the Date argument.
Like
if(date1.compareTo(date2)>0)

An alternative is Joda-Time.
Use DateTime
DateTime date = new DateTime(new Date());
date.isBeforeNow();
or
date.isAfterNow();

// Get calendar set to the current date and time
Calendar cal = Calendar.getInstance();
// Set time of calendar to 18:00
cal.set(Calendar.HOUR_OF_DAY, 18);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
// Check if current time is after 18:00 today
boolean afterSix = Calendar.getInstance().after(cal);
if (afterSix) {
System.out.println("Go home, it's after 6 PM!");
}
else {
System.out.println("Hello!");
}

The other answers are generally correct and all outdated. Do use java.time, the modern Java date and time API, for your date and time work. With java.time your job has also become a lot easier compared to the situation when this question was asked in February 2014.
String dateTimeString = "2014-01-16T10:25:00";
LocalDateTime dateTime = LocalDateTime.parse(dateTimeString);
LocalDateTime now = LocalDateTime.now(ZoneId.systemDefault());
if (dateTime.isBefore(now)) {
System.out.println(dateTimeString + " is in the past");
} else if (dateTime.isAfter(now)) {
System.out.println(dateTimeString + " is in the future");
} else {
System.out.println(dateTimeString + " is now");
}
When running in 2020 output from this snippet is:
2014-01-16T10:25:00 is in the past
Since your string doesn’t inform of us any time zone or UTC offset, we need to know what was understood. The code above uses the device’ time zone setting. For a known time zone use like for example ZoneId.of("Asia/Ulaanbaatar"). For UTC specify ZoneOffset.UTC.
I am exploiting the fact that your string is in ISO 8601 format. The classes of java.time parse the most common ISO 8601 variants without us having to give any formatter.
Question: For Android development doesn’t java.time require Android API level 26?
java.time works nicely on both older and newer Android devices. It just requires at least Java 6.
In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.
Links
Oracle tutorial: Date Time explaining how to use java.time.
Java Specification Request (JSR) 310, where java.time was first described.
ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
ThreeTenABP, Android edition of ThreeTen Backport
Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.
Wikipedia article: ISO 8601

how to convert milliseconds to date format in android?

I have milliseconds.
I need it to be converted to date format of
example:
23/10/2011
How to achieve it?

Just Try this Sample code:-
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class Test {
/**
* Main Method
*/
public static void main(String[] args) {
System.out.println(getDate(82233213123L, "dd/MM/yyyy hh:mm:ss.SSS"));
}
/**
* Return date in specified format.
* #param milliSeconds Date in milliseconds
* #param dateFormat Date format
* #return String representing date in specified format
*/
public static String getDate(long milliSeconds, String dateFormat)
{
// Create a DateFormatter object for displaying date in specified format.
SimpleDateFormat formatter = new SimpleDateFormat(dateFormat);
// Create a calendar object that will convert the date and time value in milliseconds to date.
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(milliSeconds);
return formatter.format(calendar.getTime());
}
}

Convert the millisecond value to Date instance and pass it to the choosen formatter.
SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
String dateString = formatter.format(new Date(dateInMillis)));

public static String convertDate(String dateInMilliseconds,String dateFormat) {
return DateFormat.format(dateFormat, Long.parseLong(dateInMilliseconds)).toString();
}
Call this function
convertDate("82233213123","dd/MM/yyyy hh:mm:ss");

tl;dr
Instant.ofEpochMilli( myMillisSinceEpoch ) // Convert count-of-milliseconds-since-epoch into a date-time in UTC (`Instant`).
.atZone( ZoneId.of( "Africa/Tunis" ) ) // Adjust into the wall-clock time used by the people of a particular region (a time zone). Produces a `ZonedDateTime` object.
.toLocalDate() // Extract the date-only value (a `LocalDate` object) from the `ZonedDateTime` object, without time-of-day and without time zone.
.format( // Generate a string to textually represent the date value.
DateTimeFormatter.ofPattern( "dd/MM/uuuu" ) // Specify a formatting pattern. Tip: Consider using `DateTimeFormatter.ofLocalized…` instead to soft-code the formatting pattern.
) // Returns a `String` object.
java.time
The modern approach uses the java.time classes that supplant the troublesome old legacy date-time classes used by all the other Answers.
Assuming you have a long number of milliseconds since the epoch reference of first moment of 1970 in UTC, 1970-01-01T00:00:00Z…
Instant instant = Instant.ofEpochMilli( myMillisSinceEpoch ) ;
To get a date requires a time zone. For any given moment, the date varies around the globe by zone.
ZoneId z = ZoneId.of( "Pacific/Auckland" ) ;
ZonedDateTime zdt = instant.atZone( z ) ; // Same moment, different wall-clock time.
Extract a date-only value.
LocalDate ld = zdt.toLocalDate() ;
Generate a String representing that value using standard ISO 8601 format.
String output = ld.toString() ;
Generate a String in custom format.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu" ) ;
String output = ld.format( f ) ;
Tip: Consider letting java.time automatically localize for you rather than hard-code a formatting pattern. Use the DateTimeFormatter.ofLocalized… methods.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 brought some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android (26+) bundle implementations of the java.time classes.
For earlier Android (<26), the process of API desugaring brings a subset of the java.time functionality not originally built into Android.
If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

try this code might help, modify it suit your needs
SimpleDateFormat format = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy");
Date d = format.parse(fileDate);

DateFormat.getDateInstance().format(dateInMS);

i finally find normal code that works for me
Long longDate = Long.valueOf(date);
Calendar cal = Calendar.getInstance();
int offset = cal.getTimeZone().getOffset(cal.getTimeInMillis());
Date da = new Date();
da = new Date(longDate-(long)offset);
cal.setTime(da);
String time =cal.getTime().toLocaleString();
//this is full string
time = DateFormat.getTimeInstance(DateFormat.MEDIUM).format(da);
//this is only time
time = DateFormat.getDateInstance(DateFormat.MEDIUM).format(da);
//this is only date

Short and effective:
DateFormat.getDateTimeInstance().format(new Date(myMillisValue))

Coverting epoch format to SimpleDateFormat in Android (Java / Kotlin)
input: 1613316655000
output: 2021-02-14T15:30:55.726Z
In Java
long milliseconds = 1613316655000L;
Date date = new Date(milliseconds);
String mobileDateTime = Utils.getFormatTimeWithTZ(date);
//method that returns SimpleDateFormat in String
public static String getFormatTimeWithTZ(Date currentTime) {
SimpleDateFormat timeZoneDate = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.getDefault());
return timeZoneString = timeZoneDate.format(currentTime);
}
In Kotlin
var milliseconds = 1613316655000L
var date = Date(milliseconds)
var mobileDateTime = Utils.getFormatTimeWithTZ(date)
//method that returns SimpleDateFormat in String
fun getFormatTimeWithTZ(currentTime:Date):String {
val timeZoneDate = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.getDefault())
return timeZoneString = timeZoneDate.format(currentTime)
}

Latest solution in Kotlin:
private fun getDateFromMilliseconds(millis: Long): String {
val dateFormat = "MMMMM yyyy"
val formatter = SimpleDateFormat(dateFormat, Locale.getDefault())
val calendar = Calendar.getInstance()
calendar.timeInMillis = millis
return formatter.format(calendar.time)
}
We need to add Locale as an argument of SimpleDateFormat or use LocalDate. Locale.getDefault() is a great way to let JVM automatically get the current location timezone.

public class LogicconvertmillistotimeActivity extends Activity {
/** Called when the activity is first created. */
EditText millisedit;
Button millisbutton;
TextView millistextview;
long millislong;
String millisstring;
int millisec=0,sec=0,min=0,hour=0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
millisedit=(EditText)findViewById(R.id.editText1);
millisbutton=(Button)findViewById(R.id.button1);
millistextview=(TextView)findViewById(R.id.textView1);
millisbutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
millisbutton.setClickable(false);
millisec=0;
sec=0;
min=0;
hour=0;
millisstring=millisedit.getText().toString().trim();
millislong= Long.parseLong(millisstring);
Calendar cal = Calendar.getInstance();
SimpleDateFormat formatter = new SimpleDateFormat("HH:mm:ss");
if(millislong>1000){
sec=(int) (millislong/1000);
millisec=(int)millislong%1000;
if(sec>=60){
min=sec/60;
sec=sec%60;
}
if(min>=60){
hour=min/60;
min=min%60;
}
}
else
{
millisec=(int)millislong;
}
cal.clear();
cal.set(Calendar.HOUR_OF_DAY,hour);
cal.set(Calendar.MINUTE,min);
cal.set(Calendar.SECOND, sec);
cal.set(Calendar.MILLISECOND,millisec);
String DateFormat = formatter.format(cal.getTime());
// DateFormat = "";
millistextview.setText(DateFormat);
}
});
}
}

I've been looking for an efficient way to do this for quite some time and the best I've found is:
DateFormat.getDateInstance(DateFormat.SHORT).format(new Date(millis));
Advantages:
It's localized
Been in Android since API 1
Very simple
Disadvantages:
Limited format options. FYI: SHORT is only a 2 digit year.
You burn a Date object every time. I've looked at source for the other options and this is a fairly minor compared to their overhead.
You can cache the java.text.DateFormat object, but it's not threadsafe. This is OK if you are using it on the UI thread.

This is the easiest way using Kotlin
private const val DATE_FORMAT = "dd/MM/yy hh:mm"
fun millisToDate(millis: Long) : String {
return SimpleDateFormat(DATE_FORMAT, Locale.US).format(Date(millis))
}

public static Date getDateFromString(String date) {
Date dt = null;
if (date != null) {
for (String sdf : supportedDateFormats) {
try {
dt = new Date(new SimpleDateFormat(sdf).parse(date).getTime());
break;
} catch (ParseException pe) {
pe.printStackTrace();
}
}
}
return dt;
}
public static Calendar getCalenderFromDate(Date date){
Calendar cal =Calendar.getInstance();
cal.setTime(date);return cal;
}
public static Calendar getCalenderFromString(String s_date){
Date date = getDateFromString(s_date);
Calendar cal = getCalenderFromDate(date);
return cal;
}
public static long getMiliSecondsFromString(String s_date){
Date date = getDateFromString(s_date);
Calendar cal = getCalenderFromDate(date);
return cal.getTimeInMillis();
}

public static String toDateStr(long milliseconds, String format)
{
Date date = new Date(milliseconds);
SimpleDateFormat formatter = new SimpleDateFormat(format, Locale.US);
return formatter.format(date);
}

Use SimpleDateFormat for Android N and above. Use the calendar for earlier versions
for example:
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
fileName = new SimpleDateFormat("yyyy-MM-dd-hh:mm:ss").format(new Date());
Log.i("fileName before",fileName);
}else{
Calendar cal = Calendar.getInstance();
cal.add(Calendar.MONTH,1);
String zamanl =""+cal.get(Calendar.YEAR)+"-"+cal.get(Calendar.MONTH)+"-"+cal.get(Calendar.DAY_OF_MONTH)+"-"+cal.get(Calendar.HOUR_OF_DAY)+":"+cal.get(Calendar.MINUTE)+":"+cal.get(Calendar.SECOND);
fileName= zamanl;
Log.i("fileName after",fileName);
}
Output:
fileName before: 2019-04-12-07:14:47 // use SimpleDateFormat
fileName after: 2019-4-12-7:13:12 // use Calender

fun convertLongToTimeWithLocale(){
val dateAsMilliSecond: Long = 1602709200000
val date = Date(dateAsMilliSecond)
val language = "en"
val formattedDateAsDigitMonth = SimpleDateFormat("dd/MM/yyyy", Locale(language))
val formattedDateAsShortMonth = SimpleDateFormat("dd MMM yyyy", Locale(language))
val formattedDateAsLongMonth = SimpleDateFormat("dd MMMM yyyy", Locale(language))
Log.d("month as digit", formattedDateAsDigitMonth.format(date))
Log.d("month as short", formattedDateAsShortMonth.format(date))
Log.d("month as long", formattedDateAsLongMonth.format(date))
}
output:
month as digit: 15/10/2020
month as short: 15 Oct 2020
month as long : 15 October 2020
You can change the value defined as 'language' due to your require. Here is the all language codes:
Java language codes

Compare two dates in Java

I need to compare two dates in java. I am using the code like this:
Date questionDate = question.getStartDate();
Date today = new Date();
if(today.equals(questionDate)){
System.out.println("Both are equals");
}
This is not working. The content of the variables is the following:
questionDate contains 2010-06-30 00:31:40.0
today contains Wed Jun 30 01:41:25 IST 2010
How can I resolve this?

Date equality depends on the two dates being equal to the millisecond. Creating a new Date object using new Date() will never equal a date created in the past. Joda Time's APIs simplify working with dates; however, using the Java's SDK alone:
if (removeTime(questionDate).equals(removeTime(today))
...
public Date removeTime(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
return cal.getTime();
}

I would use JodaTime for this. Here is an example - lets say you want to find the difference in days between 2 dates.
DateTime startDate = new DateTime(some_date);
DateTime endDate = new DateTime(); //current date
Days diff = Days.daysBetween(startDate, endDate);
System.out.println(diff.getDays());
JodaTime can be downloaded from here.

It's not clear to me what you want, but I'll mention that the Date class also has a compareTo method, which can be used to determine with one call if two Date objects are equal or (if they aren't equal) which occurs sooner. This allows you to do something like:
switch (today.compareTo(questionDate)) {
case -1: System.out.println("today is sooner than questionDate"); break;
case 0: System.out.println("today and questionDate are equal"); break;
case 1: System.out.println("today is later than questionDate"); break;
default: System.out.println("Invalid results from date comparison"); break;
}
It should be noted that the API docs don't guarantee the results to be -1, 0, and 1, so you may want to use if-elses rather than a switch in any production code. Also, if the second date is null, you'll get a NullPointerException, so wrapping your code in a try-catch may be useful.

The easiest way to compare two dates is converting them to numeric value (like unix timestamp).
You can use Date.getTime() method that return the unix time.
Date questionDate = question.getStartDate();
Date today = new Date();
if((today.getTime() == questionDate.getTime())) {
System.out.println("Both are equals");
}

java.time
In Java 8 there is no need to use Joda-Time as it comes with a similar new API in the java.time package. Use the LocalDate class.
LocalDate date = LocalDate.of(2014, 3, 18);
LocalDate today = LocalDate.now();
Boolean isToday = date.isEqual( today );
You can ask for the span of time between the dates with Period class.
Period difference = Period.between(date, today);
LocalDate is comparable using equals and compareTo as it holds no information about Time and Timezone.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

it is esy using time.compareTo(currentTime) < 0
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
public class MyTimerTask {
static Timer singleTask = new Timer();
#SuppressWarnings("deprecation")
public static void main(String args[]) {
// set download schedule time
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 9);
calendar.set(Calendar.MINUTE, 54);
calendar.set(Calendar.SECOND, 0);
Date time = (Date) calendar.getTime();
// get current time
Date currentTime = new Date();
// if current time> time schedule set for next day
if (time.compareTo(currentTime) < 0) {
time.setDate(time.getDate() + 1);
} else {
// do nothing
}
singleTask.schedule(new TimerTask() {
#Override
public void run() {
System.out.println("timer task is runing");
}
}, time);
}
}

The following will return true if two Calendar variables have the same day of the year.
public boolean isSameDay(Calendar c1, Calendar c2){
final int DAY=1000*60*60*24;
return ((c1.getTimeInMillis()/DAY)==(c2.getTimeInMillis()/DAY));
} // end isSameDay

Here is an another answer:
You need to format the tow dates to fit the same fromat to be able to compare them as string.
Date questionDate = question.getStartDate();
Date today = new Date();
SimpleDateFormat dateFormatter = new SimpleDateFormat ("yyyy/MM/dd");
String questionDateStr = dateFormatter.format(questionDate);
String todayStr = dateFormatter.format(today);
if(questionDateStr.equals(todayStr)) {
System.out.println("Both are equals");
}

public static double periodOfTimeInMillis(Date date1, Date date2) {
return (date2.getTime() - date1.getTime());
}
public static double periodOfTimeInSec(Date date1, Date date2) {
return (date2.getTime() - date1.getTime()) / 1000;
}
public static double periodOfTimeInMin(Date date1, Date date2) {
return (date2.getTime() - date1.getTime()) / (60 * 1000);
}
public static double periodOfTimeInHours(Date date1, Date date2) {
return (date2.getTime() - date1.getTime()) / (60 * 60 * 1000);
}
public static double periodOfTimeInDays(Date date1, Date date2) {
return (date2.getTime() - date1.getTime()) / (24 * 60 * 60 * 1000L);
}

This is a very old post though sharing my work. Here is a little trick to do so
DateTime dtStart = new DateTime(Dateforcomparision);
DateTime dtNow = new DateTime(); //current date
if(dtStart.getMillis() <= dtNow.getMillis())
{
//to do
}
use comparator as per your requirement

in my case, I just had to do something like this :
date1.toString().equals(date2.toString())
And it worked!

It works best....
Calendar cal1 = Calendar.getInstance();
Calendar cal2 = Calendar.getInstance();
cal1.setTime(date1);
cal2.setTime(date2);
boolean sameDay = cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) && cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR);

Here's what you can do for say yyyy-mm-dd comparison:
GregorianCalendar gc= new GregorianCalendar();
gc.setTimeInMillis(System.currentTimeMillis());
gc.roll(GregorianCalendar.DAY_OF_MONTH, true);
Date d1 = new Date();
Date d2 = gc.getTime();
SimpleDateFormat sf= new SimpleDateFormat("yyyy-MM-dd");
if(sf.format(d2).hashCode() < sf.format(d1).hashCode())
{
System.out.println("date 2 is less than date 1");
}
else
{
System.out.println("date 2 is equal or greater than date 1");
}

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.