I'm creating a string out from current time and I wanted to convert it to timestamp again, but the thing is, that it's subtracts 2 hours while converting.
This is the steps I'm doing -
DateTimeFormatterBuilder dateTimeFormatterBuilder = new DateTimeFormatterBuilder().append(DateTimeFormatter.ofPattern("uuuu-MM-dd")).appendLiteral(" ")
.append(DateTimeFormatter.ofPattern("HH:mm:ss")).parseLenient();
long ts = Clock.systemUTC().millis();
System.out.println(ts);
Instant instant = Instant.ofEpochMilli(ts);
ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(instant, ZoneOffset.UTC);
String str = zonedDateTime.format(dateTimeFormatterBuilder.toFormatter());
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
long timestamp = simpleDateFormat.parse(str).getTime();
System.out.println(timestamp);
} catch (ParseException e) {
e.printStackTrace();
}
output -
1639065502667
1639058302000
(2021-12-09 15:58:22
2021-12-09 13:58:22)
why is the diff of the 2 hours?
how can I parse it so that the outputs will be equal?
tl;dr
Trying to understand Date, Calendar, and SimpleDateFormat is a huge waste of time. Use only their replacements, the java.time classes.
LocalDateTime // Represent a date with time-of-day, but lacking the context of a time zone or offset-from-UTC. So *not* a moment, *not* a point on the timeline.
.parse( // Parse your text string input into a date-time object.
"2021-12-09 15:58:22" // Your input of date with time-of-day but no offset/zone.
.replace( " " , "T" ) // Replace SPACE with a `T` to comply with standard ISO 8601 format.
) // Returns a `LocalDateTime` object.
.atZone( // Place that date-with-time into the context a particular time zone.
ZoneId.of( "America/Montreal" ) // Specify a time zone by its `Continent/Region` name.
) // Returns a `ZonedDateTime` object, a date with time-of-day as seen through the wall-clock time used by the people of a particular region. This *does* represent a moment, *is* a specific point on the timeline.
.toInstant() // Adjust from time zone to UTC (an offset of zero hours-minutes-seconds). This represents the very same moment as the `ZonedDateTime` object above, but as seen through a different wall-clock time.
.toEpochMilli() // Get a count of milliseconds from first moment of 1970 in UTC (1970-01-01T00:00Z) to the moment of our `Instant` object (& `ZonedDateTime` object).
See this code run live at IdeOne.com. There you can click fork to make a copy, alter, and run.
1639083502000
Avoid legacy date-time classes
Regarding your specific question about a two hour difference, the obvious cause would be a time zone difference.
Parsing incomplete information
Your parsing, SimpleDateFormat("yyyy-MM-dd HH:mm:ss") is something of a wild card. The result will be a java.util.Date object, which represents a moment, a date with time-of-day as seen with an offset of zero. But your input lacks an indicator of offset or zone. As commented by Sotirios Delimanolis, you are parsing with partial input, with incomplete information.
So some default zone/offset will be applied. I do not know what zone or offset in particular, because I do not care. That terrible class is tragically flawed, and should be avoided.
Also, yet another problem with the Date class is that its toString method has the anti-feature of applying the JVM’s current default time zone to adjust away from the UTC value represented by that class. Very confusing, as this creates the illusion of that zone being a part of Date object but it is not. As I said, a terrible class, tragically flawed.
Use only java.time classes instead.
java.time
Understand that a date with time-of-day is inherently ambiguous, is not a moment.
If you are tracking 4 PM on the 9th, we do not know if that means 4 PM in Tokyo Japan, 4 PM in Toulouse France, or 4 PM in Toledo Ohio US — three very different moments that happen several hours apart.
LocalDateTime ldt = LocalDateTime.parse( "2021-12-09 16:00:00" ) ;
To track a moment, a point on the timeline, you must place ne date-with-time in the context of an offset from UTC or of a time zone.
An offset is merely a number of hours-minutes-seconds ahead or behind the baseline of modern timekeeping, the prime meridian at Royal Observatory, Greenwich.
A time zone is much more. A time zone is a named history of the past, present, and future changes to the offset used by the people of a particular region. Each zone has a name in format of Continent/Region such as Europe/Berlin or Asia/Tokyo.
To track moments as seen in UTC, with an offset of zero, use Instant.
Instant instant = Instant.now() ;
To see that same moment through the wall-clock time used by people in a region, apply a ZoneId to get a ZonedDateTime.
ZoneId z = ZoneId.of( "America/Edmonton" ) ;
ZonedDateTime zdt = instant.atZone( z ) ;
As for your use of SimpleDateFormat, Date, and Calendar, don’t. Avoid these legacy date-time classes. Hey were designed by people who did not understand date-time handling. They were supplanted years ago by the modern java.time classes defined in JSR 310. Sun, Oracle, and the JCP community all gave up on those classes. I suggest you do the same.
In your code:
long ts = Clock.systemUTC().millis();
Instant instant = Instant.ofEpochMilli(ts);
That is the same as doing this:
Instant.now().truncatedTo( ChronoUnit.MILLISECONDS )
In your code:
ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(instant, ZoneOffset.UTC);
(A) When working with mere offsets rather than time zones, use OffsetDateTime class. The ZonedDateTime class is for working with time zones.
(B) A briefer way to adjust from Instant to a zoned moment was shown above:
myInstant.atZone( z )
The answer was only setting the timezone to UTC -
DateTimeFormatterBuilder dateTimeFormatterBuilder = new DateTimeFormatterBuilder().append(DateTimeFormatter.ofPattern("uuuu-MM-dd")).appendLiteral(" ")
.append(DateTimeFormatter.ofPattern("HH:mm:ss")).parseLenient();
long ts = Clock.systemUTC().millis();
System.out.println(ts);
Instant instant = Instant.ofEpochMilli(ts);
ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(instant, ZoneOffset.UTC);
String str = zonedDateTime.format(dateTimeFormatterBuilder.toFormatter());
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
*******
simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
*******
long timestamp = simpleDateFormat.parse(str).getTime();
System.out.println(timestamp);
} catch (ParseException e) {
e.printStackTrace();
}
The dateTimeFomatter builder uses format without milliseconds and without timezone.
That's why the str value contain no information about them.
Then simpleDateFormat.parse(str) uses timezone of JVM which is UTC+02:00 in this case.
Trace what is going on:
Instant instant = Instant.now();
// => 2021-12-09 15:58:22.798 +00:00
String str = zonedDateTime.format(dateTimeFormatterBuilder.toFormatter());
// => "2021-12-09 15:58:22"
simpleDateFormat.parse(str);
// => 2021-12-09 15:58:22.000 +02:00
You just need to fix the pattern (add millis .SSS and timezone XXX parts) to make the results consistent as expected:
DateTimeFormatter.ofPattern("HH:mm:ss.SSSXXX")
// and something similar for SimpleDateFormat if needed
Parsing Instant from a custom formatted string.
This example shows how to parse Instant from serialized time assuming that there is a fixed timezone for all cases.
var serializedDateTime = "2020-01-01 10:20:30";
var zoneId = ZoneOffset.UTC; // may be any other zone
var format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
var instant = LocalDateTime
.parse(serializedDateTime, format)
// LocalDateTime is unzoned, just representation of (date + time) numbers in a single object
.atZone(zoneId)
// apply a zone to get ZonedDateTime (point in space-time on Earth)
.toInstant();
// convert to Instant (the same point adjusted to UTC+00:00)
Let me guess, your timezone is UTC+2?
simpleDateFormat.parse(str) assume that your date in current system timezone, but it is in UTC.
Related
DateTimes in different formats is always a problem for me. I have a date with the datatype string like "2021-07-25"
I want to convert this date to the datatype LocalDateTime in the format 2021-07-25T00:00:00.000-05:00. I have the get and set property like below
private LocalDateTime relationshipStatusDate;
public LocalDateTime getRelationshipStatusDate() {
return relationshipStatusDate;
}
public void setRelationshipStatusDate(LocalDateTime relationshipStatusDate) {
this.relationshipStatusDate = relationshipStatusDate;
}
public void setRelationshipStatusDate(String time) {
if (time != null) {
try {
long epochTime = Long.parseLong(time);
this.relationshipStatusDate = LocalDateTime.ofInstant(Instant.ofEpochMilli(epochTime), ZoneOffset.UTC);
} catch (NumberFormatException e){
this.relationshipStatusDate = LocalDateTime.parse(time, DateTimeFormatter.ISO_DATE_TIME);
}
}
}
and I am trying to format like below and its failing with an error "Unknown pattern letter T"
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-ddT00:00:00.000-05:00");
LocalDateTime dateTime = LocalDateTime.parse(statusDate, formatter);
Your format won't be parsable as it doesn't support default values like T00:00:00.000-05:00. You could escape literals e.g. use 'T00:00...' but that would just make the parser ignore them.
Instead, if all you get is a date then only parse a date and add the default time after that, e.g. like this:
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd")
LocalDate date = LocalDate.parse(statusDate, formatter );
LocalDateTime dateTime = date.atStartOfDay(); //"relative" representation as the absolute instant would require adding a timezone
ZonedDateTime zonedDT = date.atSTartOfDay(ZoneOffset.UTC); //"absolute" representation of instant
I want to convert this date to the datatype LocalDateTime in the format 2021-07-25T00:00:00.000-05:00.
Note the potential misconception here: LocalDateTime does NOT have a format. It represents a date and time (from a local point of reference - not in absolute terms as the timezone is missing) and provides access to individual fields such as day of month, day of week etc. but it is not formatted. Formatting is applied when you convert that date object to a string.
tl;dr
LocalDate // Represent a date-only value, without a time-of-day and without a time zone or offset-from-UTC.
.parse( "2021-07-25" ) // Parse a string in standard ISO 8601 format to instantiate a `LocalDate` object.
.atStartOfDay( // Determine the first moment of the day on that date in that zone. NB: The day does *not* always begin at 00:00, so never assume that time.
ZoneId.of( "America/Bogota" ) // Real time zones have a name in Continent/Region format. Never use 2-4 letter pseudo-zones such as `CST` or `IST`.
) // Returns a `ZonedDateTime` object, a moment in the context of a time zone.
.toOffsetDateTime() // Strips away the time zone information, leaving only a date with time-of-day in a particular offset. Returns an `OffsetDateTime` object.
.toString() // Generate text in standard ISO 8601 format.
2021-07-25T00:00-05:00
Details
LocalDateTime is the wrong class
You said:
datatype LocalDateTime in the format 2021-07-25T00:00:00.000-05:00
That is a contradiction. The -05:00 at the end of your string is an offset-from-UTC. A LocalDateTime object has no offset.
You seem to misunderstand the purpose of LocalDateTime. That class does not represent a moment as seen through the wall-clock time with an offset-from-UTC used by the people of a particular region. For that purpose, use OffsetDateTime, or preferably, ZonedDateTime.
Use documentation rather than intuition when programming with unfamiliar classes. To quote the Javadoc for LocalDateTime:
A date-time without a time-zone … such as 2007-12-03T10:15:30.
…
This class does not store or represent a time-zone. Instead, it is a description of the date, as used for birthdays, … It cannot represent an instant on the time-line …
Here is my chart to summarize the types. Three classes represent a moment, while LocalDateTime does not.
You said:
I have a date with the datatype string like "2021-07-25"
So use LocalDate to represent that value.
By default, the java.time classes use standard ISO 8601 format when parsing/generating text. So no need to specify a formatting pattern here, as your input complies with that standard.
LocalDate ld = LocalDate.parse( "2021-07-25" ) ;
You said:
I want to convert this date to … the format 2021-07-25T00:00:00.000-05:00
Your example there uses only a mere offset rather than a time zone. I suggest you use a time zone whenever possible.
An offset is simply a number of hours-minutes-seconds, nothing more. A time zone is much more. A time zone is a history of the past, present, and future changes to the offset used by people of a particular region, as decided by their politicians.
ZoneId
So specify your time zone using Continent/Region naming.
ZoneId z = ZoneId.of( "America/Cancun" );
ZonedDateTime
Let java.time determine the first moment of the day on that date as seen in that time zone. Be aware that the day does not always start at 00:00. So never hard-code that time-of-day; let java.time do the work here.
ZonedDateTime zdt = ld.atStartOfDay( z ); // Determine the first moment of the day as seen in that zone. Not always 00:00.
Generate text to represent the value inside our ZonedDateTime. The ZonedDateTime#toString method generates text in a format that wisely extends the ISO 8601 format by appending the name of the time zone in square brackets.
String output = zdt.toString();
2021-07-25T00:00-05:00[America/Cancun]
Pull all that code together.
LocalDate ld = LocalDate.parse( "2021-07-25" );
ZoneId z = ZoneId.of( "America/Cancun" );
ZonedDateTime zdt = ld.atStartOfDay( z ); // Determine the first moment of the day as seen in that zone. Not always 00:00.
String output = zdt.toString();
See this code run live at IdeOne.com.
2021-07-25T00:00-05:00[America/Cancun]
OffsetDateTime
If you insist on generating text in your stated format, while omitting the name of the time zone, use OffsetDateTime.
String output = zdt.toOffSetDateTime().toString() ;
All of these topics have been covered many times on Stack Overflow. Search to learn more.
I am trying to parse an input string to local date time.
Below is my piece of code
ZonedDateTime z = ZonedDateTime.parse("2019-11-26T19:30:00Z", MY_DATE_TIME_FORMATTER);
where
MY_DATE_TIME_FORMATTER= new DateTimeFormatterBuilder()
.parseCaseInsensitive()
.append(ISO_LOCAL_DATE)
.appendLiteral('T')
.append(ISO_LOCAL_TIME)
.appendLiteral('Z')
.appendOffset("+HH:mm", "+0000")
.toFormatter();
I get the following exception
java.time.format.DateTimeParseException: Text '2019-11-26T19:30:00Z' could not be parsed at index 19
Can you please advise on what I am doing wrong here?
Instant.parse
No formatting pattern needed.
Instant.parse( "2019-11-26T19:30:00Z" )
Your input format complies with ISO 8601 standard. That particular format has a Z on the end. That letter means UTC (an offset of zero hours-minutes-seconds), and is pronounced “Zulu”.
The Instant class in java.time represents a moment in UTC, always UTC.
Using ZonedDateTime class for that input is not the most appropriate. We have:
Instant for values that are always in UTC.
OffsetDateTime for moments where only an offset-from-UTC is known but not a time zone. Use this class for UTC values too when you need more flexibility such as generating strings in various formats. `instant.atOffset(
ZonedDateTime for values in a time zone. A time zone is a history of past, present, and future changes to the offset used by the people of a particular region.
To view that same moment adjusted to the offset used by the people of a particular region (a time zone), apply a ZoneId to get a ZonedDateTime object.
Instant instant = Instant.parse( "2019-11-26T19:30:00Z" ) ; // Default format for parsing a moment in UTC.
ZoneId z = ZoneId.of( "America/Edmonton" ) ; // A time zone is a history of past, present, and future changes to the offset used by the people of a particular region.
ZonedDateTime zdt = instant.atZone( z ) ; // Same moment, same point on the timeline, different wall-clock time.
See this code run live at IdeOne.com.
instant.toString(): 2019-11-26T19:30:00Z
zdt.toString(): 2019-11-26T12:30-07:00[America/Edmonton]
Add
.appendZoneOrOffsetId()
instead of these two lines:
.appendLiteral('Z')
.appendOffset("+HH:mm", "+0000")
The whole builder example:
MY_DATE_TIME_FORMATTER= new DateTimeFormatterBuilder()
.parseCaseInsensitive()
.append(ISO_LOCAL_DATE)
.appendLiteral('T')
.append(ISO_LOCAL_TIME)
.appendZoneOrOffsetId()
.toFormatter();
P.S. In your specific case I'd rather use the standard ISO formatter (as Hristo mentioned):
ZonedDateTime z = ZonedDateTime.parse("2019-11-26T19:30:00Z", DateTimeFormatter.ISO_ZONED_DATE_TIME);
Moreover, the ZonedDateTime::parse method will work even without the explicit formatter. Since it's used by default:
ZonedDateTime z = ZonedDateTime.parse("2019-11-26T19:30:00Z");
Use the built in ISO zoned time formatter
ZonedDateTime.parse("2019-11-26T19:30:00Z", DateTimeFormatter.ISO_ZONED_DATE_TIME);
I Have UTC String with a format (HH: mm: ss) and I need to convert the String value into device Time in the same format (HH: mm: ss) and also adding Day saving time if available I Have Tried to convert the UTC String to device time by this code but I am getting a 1 hour delay due to (day saving time).
String utcTimeString = "12:15:00"
SimpleDateFormat formatter = new SimpleDateFormat("HH: mm: ss");
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
Date value = formatter.parse(utcTimeString);
SimpleDateFormat dateFormatter = new SimpleDateFormat("HH: mm: ss");
dateFormatter.setTimeZone(TimeZone.getDefault());
utcDateString = dateFormatter.format(value);
My Time Zone is GMT-4
Expected Output: 08:15:00;
Given Output: 07:15:00;
The Answer by deHaar is generally correct, and wisely makes use of the modern java.time classes. However, I would use a slightly different approach.
tl;dr
OffsetDateTime.of( // Represent a moment as a date, a time-of-day, and an offset-from-UTC.
LocalDate.now( ZoneOffset.UTC ) , // Current date as seen right now in UTC. Beware: For any given moment, the date varies around the globe by zone.
LocalTime.parse( "12:15:00" ) , // Your specified time-of-day.
ZoneOffset.UTC // An offset of zero hours-minutes-seconds, for UTC itself.
) // Returns an `OffsetDateTime` object.
.atZoneSameInstant( // Adjust from UTC to a time zone. Same moment, different wall-clock-time.
ZoneId.of( "America/Port_of_Spain" ) ; // One of the many time zones that are behind UTC by four hours on that date.
) // Returns a `ZonedDateTime` object.
.toLocalTime() // Extract the time-of-day only, leaving behind the date and the zone.
Time zone
My Time Zone is GMT-4
Nope. That is not a time zone.
The value GMT-4 represents merely an offset-from-UTC. A number of hours-minutes-seconds ahead or behind the UTC baseline.
A time zone is much more. A time zone has a name, and represents the history of past, present, and future changes the offset used by the people of a particular region. Therefore, a time zone is always preferable to a mere offset.
Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "Africa/Casablanca" ) ;
If your time zone is currently four hours behind UTC, you must be in a time zone such as America/Aruba, America/Puerto_Rico, America/Manaus, America/Martinique, etc.
ZoneId z = ZoneId.of( "America/Martinique" ) ;
UTC
I Have UTC String with a format (HH: mm: ss)
Nope.
A value such as "12:15:00" cannot be said to be a value in UTC. Without a date, that value has no real meaning. A moment consists of three parts:
a date,
a time-of-day, and
an offset/zone.
Saying "noon in UTC" only gives us 2 of the 3 parts. The date is missing.
Today… what a concept
Perhaps you want to apply that time-of-day to the current date as seen in UTC.
LocalDate todayUTC = LocalDate.now( ZoneOffset.UTC ) ;
Just keep in mind that for any given moment the date varies around the globe by zone. At this very moment, the date is “tomorrow“ in Tokyo Japan while still being “yesterday” in Toledo Ohio US.
OffsetDateTime
Combine all three into a OffsetDateTime object: date, time-of-day, and offset/zone.
LocalTime localTime = LocalTime.parse( "12:15:00" ) ;
OffsetDateTime odt = OffsetDateTime.of( todayUTC , localTime, ZoneOffset.UTC ) ;
ZonedDateTime
Adjust from UTC to your particular time zone. Same moment, same simultaneous point on the timeline, different wall-clock time. Apply a ZoneId to get a ZonedDateTime object. The time zone nows about if and when Daylight Saving Time (DST) applies for this particular zone, and adjusts accordingly.
ZoneId z = ZoneId.of( "America/Martinique" ) ;
ZonedDateTime zdt = odt.atZoneSameInstant( z ) ;
Wrong approach
You should not be adding/subtracting some number of hours from a LocalTime. On some dates in some zones, a particular time-of-day may not exist. For example, for Daylight Saving Time, on the day of "Spring-ahead", in the United States, a time-of-day of 02:15:00 does not exist, as the clock jumps ahead from 02:00:00 to 03:00:00.
The correct approach using the ZonedDateTime class will automatically adjust accordingly.
You can use java.time, the modern date time API, and parse the time String to a moment in time, that is an Instant.
Then use ZonedDateTime objects to apply a certain time zone, which may be done in different ways, I show you one of them here:
public static void main(String[] args) {
// the source is just a time, but to correctly convert it, you need a date
String utcTime = "12:15:00";
// take today's date
LocalDate today = LocalDate.now();
// create a parseable date time String
String parseableDateTime = today.format(DateTimeFormatter.ISO_DATE) + "T" + utcTime + "Z";
// then create an Instant parsing the date time String
Instant instant = Instant.parse(parseableDateTime);
// get the ZoneId of UTC in order to have the time in UTC
ZoneId utc = ZoneId.of("UTC");
// do the same with your ZoneOffset of -4 Hours
ZoneId gmtMinusFour = ZoneId.ofOffset("GMT", ZoneOffset.ofHours(-4));
// create a UTC ZonedDateTime of the instant and the UTC ZoneID
ZonedDateTime utcZdt = ZonedDateTime.ofInstant(instant, utc);
// then use that ZonedDateTime to convert it to a time with your ZoneId
ZonedDateTime gmtMinusFourZdt = utcZdt.withZoneSameInstant(gmtMinusFour);
// finally print both ZonedDateTimes in order to compare them
System.out.println("UTC time is:\t\t"
+ utcZdt.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
System.out.println("GMT-4 time is:\t\t"
+ gmtMinusFourZdt.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
// then just get the time part of the converted ZonedDateTime
LocalTime localTime = gmtMinusFourZdt.toLocalTime();
// and print it
System.out.println("Converted time is:\t"
+ localTime.format(DateTimeFormatter.ISO_TIME));
}
Output:
UTC time is: 2019-09-24T12:15:00Z[UTC]
GMT-4 time is: 2019-09-24T08:15:00-04:00[GMT-04:00]
Converted time is: 08:15:00
There may be better solutions, but I hope this helps anyway…
I am having some issues formatting dates in Groovy. I am trying to convert a string back to a localdate and its not taking it so well....
DateTimeFormatter formatDates = DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm");
LocalDate currentLocalDate = LocalDate.now();
// modify the local date to the previous day
LocalDate previousDateLocalDate = currentLocalDate.minusDays(1)
// cast localdates to strings
String startDateString = previousDateLocalDate.toString() + " 00:00"
String endDateString = previousDateLocalDate.toString() + " 23:59"
// cast strings to localdates
LocalDate startDateLocalDate = LocalDate.parse(startDateString, formatDates);
The output is only showing what was in the previousDateLocalDate variable :
2019-03-06
I am not sure why its dropping the hh:mm. Could it be my format or is my syntax wrong. Any ideas would be greatly appreciated. Is it possible when I subtract a day off from my current day to just format it how I need it to be there instead or set the format when I create the LocalDate.now()?
-Thanks
Edit 1: Let me also add that the minusDays may vary so there might be a better way to get the previous day before yesterday but in some cases it might be 7, 11, etc...
Specify time zone explicitly
You should always specify explicitly the desired/expected time zone when calling now. For any given moment, the date varies around the globe by time zone. It might be “tomorrow” in Tokyo Japan while “yesterday” in Casablanca Morocco. When you omit the zone, the JVM’s current default zone is implicitly applied at runtime – so your results may vary.
ZoneId z = ZoneId.of( "Africa/Casablanca" ) ; // Or `ZoneId.systemDefault` if you actually want the JVM’s current default time zone.
LocalDate ld = LocalDate.now( z ) ; // Capture the current date as seen in the wall-clock time used by the people of a particular region (a time zone).
LocalDate
LocalDate class represents only a date, without time-of-day and without time zone or offset-from-UTC.
If you wish to combine a time-of-day with a date, use one of the other classes.
Date-time math
The java.time classes offer plus… and minus… methods for adding or subtracting a span of time.
LocalDate yesterday = ld.minusDays( 1 ) ;
First moment of the day
Apparently you want the first moment of a date. A couple things to understand here. Firstly, a time zone is needed. As discussed above, a new day dawns at different moments around the globe by zone. Secondly, do not assume the day starts at 00:00:00. Anomalies such as Daylight Saving Time (DST) means the day on some dates in same zones may start at another time, such as 01:00:00. Let java.time determine the first moment.
ZonedDateTime zdt = ld.atStartOfDay( z ) ; // Let java.time determine the first moment of the day.
Half-Open
Apparently you want the end of day. Tracking the last moment of the day is problematic. For example, your 23:59 text will miss any moment of that last minute of the day.
Generally, a better approach to tracking spans of time is the Half-Open approach where the beginning is inclusive while the ending is exclusive. So a day starts with the first moment of the day and runs up to, but does not include, the first moment of the next day.
ZonedDateTime start = ld.atStartOfDay( z ) ; // Start of today.
ZonedDateTime stop = ld.plusDays( 1 ).atStartOfDay( z ) ; // Start of tomorrow.
DateTimeFormatter
To generate strings representing your date-time object’s value, use a DateTimeFormatter object. I’ll not cover that here, as it has been covered many many many times already on Stack Overflow.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM-dd HH:mm" ) ;
String output = zdt.format( f ) ; // Generate text representing the value of this `ZonedDateTime` object.
Keep in mind that date-time objects do not have a “format”, only a textual representation of a date-time object’s value has a format. Do not conflate the string object with the date-time object. A date-time object can parse a string, and can generate a string, but is not itself a string.
try this tool
import grails.gorm.transactions.Transactional
import org.springframework.stereotype.Component
import java.time.LocalDate
import java.time.Period
import java.time.ZoneId
import java.time.chrono.ChronoLocalDate
import java.time.chrono.Chronology
import java.time.chrono.MinguoChronology
import java.time.format.DateTimeFormatter
import java.time.format.DateTimeFormatterBuilder
import java.time.format.DecimalStyle
import java.time.temporal.TemporalAccessor
import java.time.temporal.TemporalAdjusters
Date mgStringToDate(String mgString, String separator = "/") {
if(mgString){
Locale locale = Locale.getDefault(Locale.Category.FORMAT);
Chronology chrono = MinguoChronology.INSTANCE;
DateTimeFormatter df = new DateTimeFormatterBuilder().parseLenient()
.appendPattern("yyy${separator}MM${separator}dd").toFormatter().withChronology(chrono)
.withDecimalStyle(DecimalStyle.of(locale));
TemporalAccessor temporal = df.parse(mgString);
ChronoLocalDate cDate = chrono.date(temporal);
Date date = Date.from(LocalDate.from(cDate).atStartOfDay(ZoneId.systemDefault()).toInstant());
return date
}else{
return null
}
}
correct date format i am looking for:- "2017-07-06T18:03:39.195+0530"
how to get the +0530 for the current date in java ?
when i am using SimpleDateFormat it is giving +0000 , while it should give +0530 .
=================================================
i have tried using below :-
SimpleDateFormat format = new SimpleDateFormat("enter code hereyyy-MM-dd HH:mm:ss.SSS Z");
String dateString = format.format(new Date());
System.out.println("value of dateString is :"+dateString);
the above code will output :-
value of dateString is :2017-07-10 06:51:27.250 +0000
while it should output : +0530
can you please tell me how can i get the +0530 offset for the above date or current date ?
tl;dr
ZonedDateTime.now( ZoneId.of( "Asia/Kolkata" ) ).toOffsetDateTime().toString()
OffsetDateTime
To directly address the Question, use the modern OffsetDateTime class.
OffsetDateTime.now().toString()
See this code run live at IdeOne.com.
odt.toString(): 2019-08-22T17:44:00.219684Z
That will generate a string representing the current moment in the offset used by the JVM’s current default time zone using standard ISO 8601 format. One difference: This method will include the optional COLON : character between hours and minutes of the offset. I suggest never omitting that character as I have seen multiple libraries break on such input, expecting the COLON to be there.
When capturing the current moment, the result may resolve to microseconds. If you prefer milliseconds, truncate, lopping off the micros.
OffsetDateTime.now().truncatedTo( ChronoUnit.MILLIS )
odtTruncated.toString(): 2019-08-22T17:44:00.219Z
That code running at IdeOne.com is in a JVM where the offset is set to zero, for UTC itself. So we see a Z at the end, a common and standard alternative to +00:00, pronounced “Zulu”.
You may want to specify your offset explicitly.
Instant instant = Instant.now() ; // Current moment in UTC.
ZoneOffset offset = ZoneId.of( "Asia/Kolkata" ).getRules().getOffset( instant ) ; // We must pass a moment. India is currently at five and a half hours ahead of UTC. But it has not always been so in the past, and may not always be so in the future.
OffsetDateTime odt = instant.atOffset( offset ) ;
odt.toString(): 2019-08-22T23:00:06.925139+05:30
I think a cleaner syntax is to use ZonedDateTime.
String output = ZonedDateTime.now( ZoneId.of( "Asia/Kolkata" ) ).toOffsetDateTime().toString() ;
2019-08-22T23:03:19.072681+05:30
ZonedDateTime
More likely you should be getting the current moment in a time zone rather than a mere offset. If so, see the Answer by RaT.
Be clear on the difference between offset and zone:
An offset-from-UTC is merely a number of hours-minutes-seconds ahead of UTC or behind UTC.
A time zone is much more. A time zone is a history of past, present, and future changes to the offset used by the people of a particular region. A zone has a name in Continent/Region format, such as America/Montreal or Africa/Tunis.
Converting
Normally, you should avoid using the terrible date-time classes such as java.util.Date and SimpleDateFormat that are now legacy. Always use Instant, OffsetDateTime, and ZonedDateTime. Never use Date & Calendar.
But if you must you must use the legacy classes when interoperating with old code not yet updated for the java.time classes, you can convert back-and-forth. This is shown in the Answer by RaT.
You can Use Java 8 DateTime API for another solution
ZoneId zone = ZoneId.systemDefault(); //It will give current System's timezone (IST for you)
Date date = new Date(); // Any date
DateTimeFormatter formatter= DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS Z", Locale.ENGLISH);
ZonedDateTime zonedTime = ZonedDateTime.ofInstant(date.toInstant(), zone);
System.out.println(zonedTime.format(formatter));
Above code will give you Date with correct Zone Offset
After a lot of searching I found that the timezone problem can be solved with Joda time API. You can use below code to achieve what I want in my question:
DateTime dateTime = DateTime.now();
System.out.println(dateTime.toString("yyyy-MM-dd'T'HH:mm:ss.SSSZ"));
It outputs the current date with proper timezone:
2017-07-10T15:01:48.319+0530
Set the timezone you need. Your code would looke like:
SimpleDateFormat format = new SimpleDateFormat("yyy-MM-dd HH:mm:ss.SSS Z");
format.setTimeZone(TimeZone.getTimeZone("IST"));
String dateString = format.format(new Date());
System.out.println("value of dateString is :"+dateString);