I am working on a date picker where there is a range of dates. I noticed that all of my dates are a day behind and while investigating the issue I narrowed down the problem to the SimpleDateFormat object. No matter what Unix time I give it it sets the date to the previous day. An example of this behaviour is
String myFormat = "MM/dd/yyyy";
SimpleDateFormat sdf = new SimpleDateFormat(myFormat);
Log.d(TAG, "Time Zone: " + cal.getTimeZone().getDisplayName());
Log.d(TAG, "Printable: " + sdf.format(0));
The output that I see in the logger is
Time Zone: UTC
Printable: 12/31/1969
Why does the formatter use December 31 instead of January 1st 1970?
Because the DateFormat also has a TimeZone (and your system isn't set to UTC). You can change it with DateFormat.setTimeZone(TimeZone). Something like
String myFormat = "MM/dd/yyyy";
SimpleDateFormat sdf = new SimpleDateFormat(myFormat);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println("Printable: " + sdf.format(0));
Output is (as you expected)
Printable: 01/01/1970
Related
I am trying to correct a date with some offset value according to the time zone. So, when I format a timestamp with a time zone offset, I expected that SimpleDateFormat will add the offset value to the time.
Here is what I tried:
package com.krishna.mytrials;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
public class DateExperiments {
public static void main(String[] args) throws Exception {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
//Date we set in UI
Date today = new Date();
//The long value
String todayBrowserLocalTimeStamp = sdf.format(today);
System.out.println(todayBrowserLocalTimeStamp);
Date todayBrowserLocalTimeStampDate = sdf.parse(todayBrowserLocalTimeStamp);
System.out.println("Today's browser local time stamp: " + todayBrowserLocalTimeStampDate);
System.out.println("And its long value:" + todayBrowserLocalTimeStampDate.getTime());
System.out.println("Date generate from long:"+ new Date(todayBrowserLocalTimeStampDate.getTime()));
//What server does to the above mid night time stamp of browser-local time zone
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
//What we get after it applied the server time zone to browser-local date
//### This is the wrong date
SimpleDateFormat sdf2 = new SimpleDateFormat();
sdf2.setTimeZone(TimeZone.getTimeZone("GMT"));
sdf2.applyPattern("yyyy-MM-dd HH:mm");
System.out.println(sdf2.format(todayBrowserLocalTimeStampDate));
String utcDateString = sdf.format(todayBrowserLocalTimeStampDate);
System.out.println("The above mid night time stamp of browser-local time zone"
+ "is converted to GMT.### The wrong one:");
System.out.println(utcDateString);
//### The wrong date constructed
Date utcDate = sdf.parse(utcDateString);
System.out.println("###Wrong date:"+utcDate);
//### The wrong long
Long utcLong = utcDate.getTime();
System.out.println("###Wrong long:"+utcLong);
// What we will do with the GMT+05:30
sdf.setTimeZone(TimeZone.getTimeZone("GMT+05:30"));
String dateToBeCorrected = sdf2.format(todayBrowserLocalTimeStampDate);
System.out.println("Date to be corrected:"+ dateToBeCorrected);
SimpleDateFormat sdf3 = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Date correctedDate = sdf3.parse(dateToBeCorrected);
System.out.println(correctedDate);
SimpleDateFormat sdf4 = new SimpleDateFormat();
sdf4.setTimeZone(TimeZone.getTimeZone("IST"));
String correctedString = sdf4.format(correctedDate);
System.out.println("Corrected date:" + formatDateToString(correctedDate,"dd MMM yyyy hh:mm:ss a", "IST"));
}
public static String formatDateToString(Date date, String format,
String timeZone) {
// null check
if (date == null) return null;
// create SimpleDateFormat object with input format
SimpleDateFormat sdf = new SimpleDateFormat(format);
// default system timezone if passed null or empty
if (timeZone == null || "".equalsIgnoreCase(timeZone.trim())) {
timeZone = Calendar.getInstance().getTimeZone().getID();
}
// set timezone to SimpleDateFormat
sdf.setTimeZone(TimeZone.getTimeZone(timeZone));
// return Date in required format with timezone as String
return sdf.format(date);
}
}
Here is the output:
2017-01-12
Today's browser local time stamp: Thu Jan 12 00:00:00 IST 2017
And its long value:1484159400000
Date generate from long:Thu Jan 12 00:00:00 IST 2017
2017-01-11 18:30
The above mid night time stamp of browser-local time zoneis converted to GMT.### The wrong one:
2017-01-11
###Wrong date:Wed Jan 11 05:30:00 IST 2017
###Wrong long:1484092800000
Date to be corrected:2017-01-11 18:30
Wed Jan 11 18:30:00 IST 2017
Corrected date:11 Jan 2017 06:30:00 PM
It is supposed add 05:30. to the date. What am I doing wrong?
You have to consider that roundtrips using formatting and parsing can loose informations. This is due to the fact that a formatted date might contain less informations than the original Date-instance had. Look at this data loss:
Original timestamp (variable todayBrowserLocalTimeStampDate) was: 2017-01-11 18:30 (in UTC) or as long: 1484175600000L
String utcDateString = sdf.format(new Date(1484175600000L));
// 2017-01-11
Date utcDate = sdf.parse(utcDateString);
Here you strip away the time part AND parse the stripped string again. Of course, the resulting new Date-instance must loose the corresponding time part, too, and cannot be the same as before.
2017-01-11 (with zero time) would be rendered in your IST-zone 5:30 hours later, that is: 2017-01-11T05:30+05:30 (remember: Date.toString() uses your IST-zone assuming that is your system zone). This is same instant as 2017-01-11T00:00Z. All is fine, only your expectation expressed in line indicated by prefix ###Wrong date is wrong.
I have a timestamp coming from an API in this format:
yyyy-MM-dd'T'HH:mm:ss.SSSSSS
I want to format it for the user in their own timezone (on android). This is what I'm doing:
String timestampFromApi = "...";
DateFormat df1 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss", Locale.ENGLISH);
Date date = df1.parse(timestampFromApi);
DateFormat df2 = new SimpleDateFormat();
Log.v(TAG, "In your timezone: " + df2.format(date));
But this prints the time in UTC. For example, if the timestamp happened at 4pm UTC time, and I am in PDT, the result is that it still prints "4pm".
I checked the timezone being used:
df2.getTimeZone()
and it does print out PDT for my device. What have I done wrong here?
Thanks
You're on the right track. You got the UTC time from the server, but now you just need to calculate the local offset when formatting. Try something like this:
private String formatTime(String timestampFromApi){
SimpleDateFormat df1 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss", Locale.ENGLISH);
df1.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = df1.parse(timestampFromApi);
Log.v(TAG, "In your timezone: " + df1.format(getAdjustedTime(date.getTime())));
}
private Date getAdjustedTime(long utcDate){
return new Date(utcDate + TimeZone.getDefault().getOffset(new Date().getTime()));
}
The getAdjustedTime() method will create a new Date object based on the UTC-offset from the local TimeZone.
Probably there will be simply and fast answer but I still cant find out why is the result of
Date date = new Date(60000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
dateStr - 01:01:00
Still one hour more. Time zone? How can I set it without it? Thanks.
Date represents a specific moment in time, not a duration. new Date(60000) does not create "one minute". See the docs for that constructor:
Initializes this Date instance using the specified millisecond value. The value is the number of milliseconds since Jan. 1, 1970 GMT.
If you want "one minute from now" you'll probably want to use the Calendar class instead, specifically the add method.
Update:
DateUtils has some useful methods that you might find useful. If you want the elapsed time in HH:mm:ss format, you might try DateUtils.formatElapsedTime. Something like:
String dateStr = DateUtils.formatElapsedTime(60);
Note that the 60 is in seconds.
Three ways to use java.util.Date to specify one minute:
1. Using SimpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC")) as shahtapa said:
Date date = new Date(60*1000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
2. Using java.util.Calendar as kabuko said:
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Other calendar.set() statements can also be used:
calendar.set(Calendar.MILLISECOND,60*1000); //one min.
calendar.set(1970,0,1,0,1,0); //one min.
3. Using these setTimeZone and Calendar ideas and forcing Calendar to
UTC Time-Zone
as Simon Nickerson said:
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Note: I had a similar issue: Date 1970-01-01 was in my case -3 600 000 milliseconds (1 hour late) java.util.Date(70,0,1).getTime() -> -3600000
I recommend to use TimeUnit
"A TimeUnit represents time durations at a given unit of granularity and provides utility methods to convert across units, and to perform timing and delay operations in these units. A TimeUnit does not maintain time information, but only helps organize and use time representations that may be maintained separately across various contexts. A nanosecond is defined as one thousandth of a microsecond, a microsecond as one thousandth of a millisecond, a millisecond as one thousandth of a second, a minute as sixty seconds, an hour as sixty minutes, and a day as twenty four hours."
http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/TimeUnit.html
Date date = new Date(); // getting actual date
date = new Date (d.getTime() + TimeUnit.MINUTES.toMillis(1)); // adding one minute to the date
I am trying to convert a formatted date String to Date object. Date String is formatted to some other timezone.
When I do sdf.parse(String) it returns me my System date object.
Code is as below,
static Date convertGMTTime(String timeZone, long longDate){
Date convertedTime = null;
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try{
Date date = new Date(longDate);
System.out.println("timezone: "+timeZone +", timestamp: "+date);
Locale locale = Locale.ENGLISH;
TimeZone destTimeZone = TimeZone.getTimeZone(timeZone);// TimeZone.getDefault();
System.out.println("Source timezone: "+destTimeZone);
/* DateFormat formatter = DateFormat.getDateTimeInstance(
DateFormat.DEFAULT,
DateFormat.DEFAULT,
locale);
formatter.setTimeZone(destTimeZone);*/
sdf.setTimeZone(destTimeZone);
String convertedDateStr = sdf.format(date);
System.out.println("convertedDateStr: "+convertedDateStr);
convertedTime = sdf.parse(convertedDateStr);
System.out.println("convertedTime: "+convertedTime + "sdf: "+sdf.getTimeZone());
}catch(Exception e){
e.printStackTrace();
}
return convertedTime;
}
I would appreciate if anyone could help and point out where I am going wrong.
Thanks in advance.
Output:
timezone: Atlantic/Cape_Verde, timestamp: Tue Jun 26 17:38:11 IST 2012
Source timezone: sun.util.calendar.ZoneInfo[id="Atlantic/Cape_Verde",offset=-3600000,dstSavings=0,useDaylight=false,transitions=6,lastRule=null]
convertedDateStr: 2012-06-26 11:08:11
convertedTime: Tue Jun 26 17:38:11 IST 2012
sdf:sun.util.calendar.ZoneInfo[id="Atlantic/Cape_Verde",offset=-3600000,dstSavings=0,useDaylight=false,transitions=6,lastRule=null]
Some more details to share, When I use another sdf object(without setting timezone for it), It do return me correct time and date but still timezone is picked from System clock
Code
static Date convertGMTTime(String timeZone, long longDate){
Date convertedTime = null;
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat sdfParse = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try{
Date date = new Date(longDate);
TimeZone destTimeZone = TimeZone.getTimeZone(timeZone);// TimeZone.getDefault();
System.out.println("Source timezone: "+destTimeZone);
sdf.setTimeZone(destTimeZone);
String convertedDateStr = sdf.format(date);
System.out.println("convertedDateStr: "+convertedDateStr );
convertedTime = sdfParse.parse(convertedDateStr,new ParsePosition(0));
System.out.println("convertedTime: "+convertedTime + "sdf: "+sdf.getTimeZone());
}catch(Exception e){
e.printStackTrace();
}
return convertedTime;
}
Output
Source timezone: sun.util.calendar.ZoneInfo[id="Atlantic/Cape_Verde",offset=-3600000,dstSavings=0,useDaylight=false,transitions=6,lastRule=null]
convertedDateStr: 2012-06-26 12:24:56
convertedTime: Tue Jun 26 12:24:56 IST 2012
sdf: sun.util.calendar.ZoneInfo[id="Atlantic/Cape_Verde",offset=-3600000,dstSavings=0,useDaylight=false,transitions=6,lastRule=null]
I understand that when I do not assign timezone to sdf it takes System time zone, but why doesn't it show time in System time zone? I shows it in timezone as it was in String but Timezone is different.
Ans when I set timezone it returns date object as per my system time irrespective of the fact that sdf has some other time zone set.
Can anyone please explain the functional behavior for sdf.parse and sdf.format.
For me sdf.setTimeZone() does have its impact when we use format and it is nullified when we use sdf.parse(). I find it quite strange.
Appreciate help in this regard.
You already have a Date (or the number of milliseconds of the Date), so there is nothing to convert. A Date doesn't have any time zone. It's a universal instant in time. The time zone is relevant only when you display this date, because the date 65647678000 could be 12:38 in some time zone, but 10:38 in some other time zone. It's also relevant when you parse the String representation of a Date, because 10:38 is 65647678000 in some time zone, but is 65657678000 in some other.
While you don't display a Date object, or parse a String to a Date, you don't need to care about time zones. And to choose the time zone used when displaying/parsing it, set the time zone of the DateFormat, and then use DateFormat.format()/DateFormat.parse() to format/parse the date.
When you use Date.toString() to display a date, it will always use your current time zone.
I find it easier to understand what I mean by not thinking of a Date as a day, a month, a year, an hour, etc., but as a moment: "when Kennedy was shot". "When Kennedy was shot" is the same moment for everyone. But if you represent the moment "when Kennedy was shot" in Dallas time zone, it's not the same result as the result you get when you represent this same moment in Paris time zone.
I need to format java XmlGregorianCalendar to "yyMMdd" string.
My implementation:
XMLGregorianCalendar date = getDate(); //getting the date
if (date != null) {
SimpleDateFormat sdf = new SimpleDateFormat("yyMMdd");
LOG.debug("Parsing date...");
LOG.debug("XML Date: " + date);
LOG.debug("XML Date timezone: " + date.getTimezone());
GregorianCalendar gc = date.toGregorianCalendar();
LOG.debug("Gregorian calendar: " + gc.toString());
LOG.debug("Gregorian calendar timezone id: " + gc.getTimeZone().getID());
Date d = gc.getTime();
LOG.debug("Date: " + d.toString());
String formatted = sdf.format(d);
LOG.debug("Formatted: " + formatted);
}
What I see in log:
Parsing date...
XML Date: 1943-04-15T00:00:00.000Z
XML Date timezone: 0
Gregorian calendar: java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="GMT+00:00",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=1943,MONTH=3,WEEK_OF_YEAR=1,WEEK_OF_MONTH=1,DAY_OF_MONTH=15,DAY_OF_YEAR=1,DAY_OF_WEEK=5,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=0,HOUR_OF_DAY=0,MINUTE=0,SECOND=0,MILLISECOND=0,ZONE_OFFSET=0,DST_OFFSET=0]
Gregorian calendar timezone id: GMT+00:00
Date: Wed Apr 14 20:00:00 EDT 1943
Formatted: 430414
April, 15 was parsed as April, 14. What I'm doing wrong? When I should set timezone?
It was parsed as midnight on April 15th UTC. It was then formatted as 8pm on April 14th EDT, which is correct as EDT is four hours behind UTC.
Note that Date.toString() always uses the local time zone - a Date object has no concept of which time zone it's in.
Your formatted value is also using the default time zone, as you haven't specified a time zone. The calendar value (gc) is in UTC, but when you format it, it will apply the time zone from the formatter (as you format the Date value, which doesn't have a time zone).
It's not clear what you were trying to achieve, but hopefully that will help. As an aside, I'd strongly recommend that you use Joda Time instead if you possibly can - it makes a lot of this much clearer.