I'm learning Java and come across this issue. I have a date string with the given format.
String dbTime = "01/01/1998 12:30:00";
final String DATE_FORMAT = "MM/dd/yyyy HH:mm:ss";
Now I wanted to initialize/create a Date object of UTC timezone.
For this, I have tried below code
SimpleDateFormat sdfAmerica = new SimpleDateFormat(DATE_FORMAT);
TimeZone utcTimeZone = TimeZone.getTimeZone("UTC");
sdfAmerica.setTimeZone(utcTimeZone);
String sDateInAmerica = sdfAmerica.format(date); // Convert to String first
Date dateInAmerica = new Date();
try {
dateInAmerica = formatter.parse(sDateInAmerica); // Create a new Date object
} catch (ParseException e) {
e.printStackTrace();
}
This will convert the time into UTC instead of just creating a date object.
01/02/1998 23:00:00
Now I'm confused as to which is the correct approach to convert the time.
I have time in string format and I have to convert it into different formats mainly UTC to PST or PST to UTC.
After some research, I found this tutorial but was unable to get the expected output.
The java.util.Date class is not optimal to start with. While it looks like a full date from the outside, it actually only represents a timestamp without storing actual timezone information.
On Java 8 and later I'd suggest to stick with the better designed java.time.* classes.
String dbTime = "01/01/1998 12:30:00";
String DATE_FORMAT = "MM/dd/yyyy HH:mm:ss";
// parsed date time without timezone information
LocalDateTime localDateTime = LocalDateTime.parse(dbTime, DateTimeFormatter.ofPattern(DATE_FORMAT));
// local date time at your system's default time zone
ZonedDateTime systemZoneDateTime = localDateTime.atZone(ZoneId.systemDefault());
// value converted to other timezone while keeping the point in time
ZonedDateTime utcDateTime = systemZoneDateTime.withZoneSameInstant(ZoneId.of("UTC"));
// timestamp of the original value represented in UTC
Instant utcTimestamp = systemZoneDateTime.toInstant();
System.out.println(utcDateTime);
System.out.println(utcTimestamp);
As you can see from the names alone there are different classes for different use-cases of dates.
java.time.LocalDateTime for example only represents a date and time without a specific timezone context and therefore can be used to parse your string value directly.
To convert timezones, you first have to convert into the a ZonedDateTime, which accepts date, time and timezone. I've intialized the sample on "systemDefault", as on most smaller apps you can use the JVM and OS'es default value to assume the current timezone.
You could also use ZoneId.of("America/Los_Angeles") directly if you want to make sure the value is interpreted as pacific time.
This value can be converted into another ZonedDateTime in another timezone, e.g. UTC.
For UTC especially you could also use the Instant class, which represents only a UTC timestamp and can also be used as a basis for most other types
I have a date that is in IST format. Which is something like the
2021-12-07T00:00:00.595+0530
I have the following code for the above output
val fromtTime = Date()
val startOfDay = fromtTime.startOfDay()
val dateFormat = SimpleDateFormat(
"yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"
)
val startOfDate = dateFormat.format(startOfDay)
startOfDay is just and extenstion function which is something like this
fun Date.startOfDay(): Date {
val now = Calendar.getInstance()
now.time = this
now.set(Calendar.HOUR_OF_DAY, 0)
now.set(Calendar.MINUTE, 0)
now.set(Calendar.SECOND, 0)
return now.time
}
But, what the backend really wants is in the below format with -8:00.
2021-12-07T00:00:00-08:00
Is there any way I can format it to have -08:00 in the end of the string whenever I select the timezone as "America/Los_Angeles", because "America/Los_Angeles" is supposed to have the timezone which is -8 hours from the GMT.
java.time
I recommend that you use java.time, the modern Java date and time API, for your date and time work. Please excuse my Java syntax.
String forBackend = LocalDate.now(ZoneId.systemDefault())
.atStartOfDay(ZoneId.of("America/Los_Angeles"))
.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME);
System.out.println(forBackend);
I ran this code in Asia/Kolkata time zone just now (within the first hour after midnight on 2021-12-08). The output was:
2021-12-08T00:00:00-08:00
A LocalDate is a date without time of day or time zone, so LocalDate.now() just gives us the current day in India (when Asia/Kolkata is our default time zone) without time of day. Then the call to atStartOfDay() gives us the start if the same date in America/Los_Angeles time zone. Finally the format you asked for is built in, so we are using the predefined formatter and not writing our own format pattern string.
When summer time (DST) begins in North America, the offset will be -07:00 instead.
This question already has answers here:
Android convert UTC Date to local timezone [duplicate]
(2 answers)
Closed 5 years ago.
I have a date String like 2017-09-16T05:06:18.157 and I want to convert it to local time (IST). In Indian Standard Time it will be around 2017-09-16 10:36:18.
With Joda-Time, I have tried to convert it to local but I was not able to do it.
Below is my code:
private String getConvertDate(String date_server) {
DateTimeFormatter inputFormatter = DateTimeFormat
.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS")
.withLocale(Locale.US);
DateTime parsed = inputFormatter.parseDateTime(date_server);
DateTimeFormatter outputFormatter = DateTimeFormat
.forPattern("yyyy-MM-dd HH:mm:ss")
.withLocale(Locale.US)
.withZone(DateTimeZone.getDefault());
return outputFormatter.print(parsed);
}
Good you found a solution with SimpleDateFormat. I'd just like to add more insights about it (basically because the old classes (Date, Calendar and SimpleDateFormat) have lots of problems and design issues, and they're being replaced by the new APIs).
The input String (2017-09-16T05:06:18.157) contains only the date (year/month/day) and time (hour/minute/second/millisecond), but no timezone information. So, when calling parseDateTime, Joda-Time just assumes that it's in the JVM default timezone.
If you know that the input is in UTC, but the input itself has no information about it, you must tell it. One way is to set in the formatter:
// set the formatter to UTC
DateTimeFormatter inputFormatter = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS")
.withZone(DateTimeZone.UTC);
// DateTime will be in UTC
DateTime parsed = inputFormatter.parseDateTime("2017-09-16T05:06:18.157");
Another alternative is to first parse the input to a org.joda.time.LocalDateTime (a class that represents a date and time without a timezone), and then convert it to a DateTime in UTC:
// parse to LocalDateTime
DateTime = parsed = LocalDateTime.parse("2017-09-16T05:06:18.157")
// convert to a DateTime in UTC
.toDateTime(DateTimeZone.UTC);
Both produces the same DateTime, corresponding to UTC 2017-09-16T05:06:18.157Z.
To format it to "IST timezone" (which is actually not a timezone - more on that below), you can also set the timezone in the formatter:
// convert to Asia/Kolkata
DateTimeFormatter outputFormatter = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss")
.withZone(DateTimeZone.forID("Asia/Kolkata"));
System.out.println(outputFormatter.print(parsed));
Or you can convert the DateTime to another timezone, using the withZone() method:
DateTimeFormatter outputFormatter = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss");
// convert to Asia/Kolkata
System.out.println(outputFormatter.print(parsed.withZone(DateTimeZone.forID("Asia/Kolkata"))));
Both will print:
2017-09-16 10:36:18
In your code you're using DateTimeZone.getDefault(), that gets the JVM default timezone (with some tricky details). But the default timezone can be changed without notice, even at runtime, so it's always better to specify which one you want to use.
Also, keep in mind that short names like IST are not real timezones. Always prefer to use IANA timezones names (always in the format Region/City, like Asia/Kolkata or Europe/Berlin).
Avoid using the 3-letter abbreviations (like IST or PST) because they are ambiguous and not standard. Just check in this list that IST can be "India Standard Time", "Israel Standard Time" and "Irish Standard Time".
You can get a list of available timezones (and choose the one that fits best your system) by calling DateTimeZone.getAvailableIDs().
Java new Date/Time API
Joda-Time is in maintainance mode and is being replaced by the new APIs, so I don't recommend start a new project with it. Even in joda's website it says: "Note that Joda-Time is considered to be a largely “finished” project. No major enhancements are planned. If using Java SE 8, please migrate to java.time (JSR-310).".
If you can't (or don't want to) migrate from Joda-Time to the new API, you can ignore this section.
In Android you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes. To make it work, you'll also need the ThreeTenABP (more on how to use it here).
This new API has lots of different date/time types for each situation.
First, you can parse the input to a org.threeten.bp.LocalDateTime, then I use a org.threeten.bp.ZoneOffset to convert it to UTC, resulting in a org.threeten.bp.OffsetDateTime.
Then, I use a org.threeten.bp.ZoneId to convert this to another timezone, and use a org.threeten.bp.format.DateTimeFormatter to format it (this is basically what's suggested by #Ole V.V's comment - just to show how straightforward it is, as there aren't anything much different to do):
// parse to LocalDateTime
OffsetDateTime parsed = LocalDateTime.parse("2017-09-16T05:06:18.157")
// convert to UTC
.atOffset(ZoneOffset.UTC);
// convert to Asia/Kolkata
ZoneId zone = ZoneId.of("Asia/Kolkata");
DateTimeFormatter outputFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
System.out.println(outputFormatter.format(parsed.atZoneSameInstant(zone)));
The output is:
2017-09-16 10:36:18
try this code:
String serverdateFormat = "yyyy-MM-dd'T'HH:mm:ss'Z'";
public String convertServerDateToUserTimeZone(String serverDate) {
String ourdate;
try {
SimpleDateFormat formatter = new SimpleDateFormat(serverdateFormat, Locale.UK);
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
Date value = formatter.parse(serverDate);
TimeZone timeZone = TimeZone.getTimeZone("Asia/Kolkata");
SimpleDateFormat dateFormatter = new SimpleDateFormat(serverdateFormat, Locale.UK); //this format changeable
dateFormatter.setTimeZone(timeZone);
ourdate = dateFormatter.format(value);
//Log.d("OurDate", OurDate);
} catch (Exception e) {
ourdate = "0000-00-00 00:00:00";
}
return ourdate;
}
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
TimeZone utcZone = TimeZone.getTimeZone("UTC");
simpleDateFormat.setTimeZone(utcZone);
Date myDate =simpleDateFormat.parse(rawQuestion.getString("Asia/Kolkata"));
simpleDateFormat.setTimeZone(TimeZone.getDefault());
String formattedDate = simpleDateFormat.format(myDate);
I have a field that is defined as TIMESTAMP WITH TIME ZONE.
The value to be saved starts off as: "09-23-2019 10:03:11 pm" in the zone of US/Hawaii.
This is what I am trying to save to the DB (all of the date information plus the Zone)
The database stores time information in UTC format.
As of now, the date is being stored in the DB so that it looks like this:
DAYS
---------------------------------------------------------------------------
23-SEP-19 10.03.11.000000 PM -05:00
23-SEP-19 10.03.11.000000 PM -05:00
During the processing, it runs through this code:
dateStr: the date (as seen above)
ZoneLoc: 'US/Hawaii'
public Calendar convDateStrWithZoneTOCalendar(String dateStr,
String ZoneLoc) throws Exception {
// convert the string sent in from user (which uses AM/PM) to one that uses military time (24HR)
// it
String formattedDate = null;
DateFormat readFormat = new SimpleDateFormat(this.getPattern());
DateFormat writeFormat = new SimpleDateFormat("MM-dd-yyyy'T'HH:mm:ss'Z'");
writeFormat.setTimeZone(TimeZone.getTimeZone(ZoneLoc));
Date date = null;
date = readFormat.parse(dateStr);
formattedDate = writeFormat.format(date);
// see if you can parse the date needed WITH the TimeZone
Date d;
SimpleDateFormat sdf = new SimpleDateFormat("MM-dd-yyyy'T'HH:mm:ss'Z'");
sdf.setTimeZone(TimeZone.getTimeZone(ZoneLoc));
d = sdf.parse(formattedDate);
Calendar cal = Calendar.getInstance();
cal.setTime(d);
system.out.println(" ZONELOC VALUE " + ZoneLoc);
system.out.println(" RETURNED VALUE " + cal );
return cal;
}
The calendar info that is returned is:
ZONELOC VALUE IS US/Hawaii
RETURNED VALUE IS
java.util.GregorianCalendar[time=1577678591000,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/Chicago",offset=-21600000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/Chicago,offset=-21600000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2019,MONTH=11,WEEK_OF_YEAR=1,WEEK_OF_MONTH=5,DAY_OF_MONTH=29,DAY_OF_YEAR=363,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=5,AM_PM=1,HOUR=10,HOUR_OF_DAY=22,MINUTE=3,SECOND=11,MILLISECOND=0,ZONE_OFFSET=-21600000,DST_OFFSET=0]
It looks as though US/Hawaii is not being set in the RETURNED VALUE.
What can I do to be sure that this gets set?
After that, I can place it in the DB and see if the setting will "stick" and not revert back to America/Chicago
Update
#Patrick H - thanks for the input. I made the change with the pattern you specified and was able to save the data. It now looks like this:
2017-08-02 13:38:49 TRACE o.h.type.descriptor.sql.BasicBinder - binding parameter [26] as [TIMESTAMP] - [java.util.GregorianCalendar[time=1569294191000,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/Chicago",offset=-21600000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/Chicago,offset=-21600000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2019,MONTH=8,WEEK_OF_YEAR=39,WEEK_OF_MONTH=4,DAY_OF_MONTH=23,DAY_OF_YEAR=266,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=4,AM_PM=1,HOUR=10,HOUR_OF_DAY=22,MINUTE=3,SECOND=11,MILLISECOND=0,ZONE_OFFSET=-21600000,DST_OFFSET=3600000]]
The data in the DB looks like this:
23-SEP-19 10.03.11.000000 PM -05:00
The Zone is still America/Chicago even through US/Hawaii was specified. How can one get US/Hawaii to stick and not revert back to America/Chicago?
According to this output:
java.util.GregorianCalendar[time=1569294191000,...
The time value above (which means 1569294191000 milliseconds since unix epoch (1970-01-01T00:00Z)) is equivalent to 09-23-2019 10:03 PM in Chicago. That's because readFormat is using the system's default timezone (which is probably America/Chicago, just check the value of TimeZone.getDefault()).
To parse the input 09-23-2019 10:03:11 pm and consider it as the local time in Hawaii, you just need to set the corresponding timezone to the SimpleDateFormat instance (in this case, to readFormat, as it needs to know in what timezone the input date is - as you didn't set any, it uses the system's default). You also don't need the other formatters (writeFormat and sdf), only one formatter can be used to get the corresponding date:
SimpleDateFormat parser = new SimpleDateFormat("MM-dd-yyyy hh:mm:ss a");
// the input is in Hawaii timezone
parser.setTimeZone(TimeZone.getTimeZone("US/Hawaii"));
Date date = parser.parse("09-23-2019 10:03:11 pm");
The date above will be equivalent to 10:03 PM in Hawaii. Actually, the date itself contains just the milliseconds from the unix epoch (date.getTime() returns 1569312191000) and has no format nor any timezone information.
You can then set it to a Calendar instance (don't forget to set the calendar's timezone):
Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("US/Hawaii"));
cal.setTime(date);
It's been some time since I used oracle's timestamp with timezone type, but I think that'll be enough to save the correct values. The value of calendar is:
java.util.GregorianCalendar[time=1569312191000,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="US/Hawaii",offset=-36000000,dstSavings=0,useDaylight=false,transitions=7,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2019,MONTH=8,WEEK_OF_YEAR=39,WEEK_OF_MONTH=4,DAY_OF_MONTH=23,DAY_OF_YEAR=266,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=4,AM_PM=1,HOUR=10,HOUR_OF_DAY=22,MINUTE=3,SECOND=11,MILLISECOND=0,ZONE_OFFSET=-36000000,DST_OFFSET=0]
Java new Date/Time API
The old classes (Date, Calendar and SimpleDateFormat) have lots of problems and design issues, and they're being replaced by the new APIs.
One of the main problems is how hard and confusing it is to work with different timezones.
If you're using Java 8, consider using the new java.time API. It's easier, less bugged and less error-prone than the old APIs.
If you're using Java <= 7, you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes. And for Android, there's the ThreeTenABP (more on how to use it here).
The code below works for both.
The only difference is the package names (in Java 8 is java.time and in ThreeTen Backport (or Android's ThreeTenABP) is org.threeten.bp), but the classes and methods names are the same.
To parse the input 09-23-2019 10:03:11 pm you can use a DateTimeFormatter and parse it to a LocalDateTime - the input has no timezone information, so we consider only the date and time, and then we can convert it to a timezone.
// parse the input
DateTimeFormatter fmt = new DateTimeFormatterBuilder()
// parse AM/PM and am/pm
.parseCaseInsensitive()
// input pattern
.appendPattern("MM-dd-yyyy hh:mm:ss a")
// use English locale for am/pm symbols
.toFormatter(Locale.ENGLISH);
LocalDateTime dt = LocalDateTime.parse("09-23-2019 10:03:11 pm", fmt);
// convert to Hawaii timezone
ZonedDateTime hawaiiDate = dt.atZone(ZoneId.of("US/Hawaii"));
The most recent JDBC drivers have support to the new API (but only for Java 8, I guess), but if you still need to work with Calendar, you can easily convert a ZonedDateTime to it:
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("US/Hawaii"));
calendar.setTimeInMillis(hawaiiDate.toInstant().toEpochMilli());
In Java 8, you can also do:
Calendar calendar = GregorianCalendar.from(hawaiiDate);
If you need interoperability with the old Calendar and Date API's, you can use the new API internally to do the calculations and convert from/to the API's when needed.
According to SimpleDateFormat, I think your formatting string is wrong. You can also see in the returned value that the month, and day are wrong. MONTH=11,DAY_OF_MONTH=29
This is what you currently have:
23-SEP-19 10.03.11.000000 PM -05:00
I think the formatting string should be: 'dd-MMM-yy hh.mm.ss.SSSSSS a Z'
It also looks like the timezone issue could be because there is a colon inside it. The documentation for SimpleDateFormat indicates it needs to be in this format instead for a RFC 822 time zone: -0500 You may find it easier to use the General time zone component instead.
I receive datetime strings with no timezone qualifier in the format:
2014-01-30 07:48:25
I know that the strings are produced by a server in Florida. Is there a way using java.util or joda Date libs to specify that the date is from Florida then parse it with the appripriate UTC offset, depending on where it falls in the calendar for daylight savings time?
Assuming you are referring to the part of Florida following EST, you can set the timezone for SimpleDateFormat and set your TimeZone to EST.
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
format.setTimeZone(TimeZone.getTimeZone("America/New_York"));
Date date = format.parse("2014-01-30 07:48:25");
Your parsed date now can be utilized by your default TimeZone of the system (or set it to your liking as we did in the first place).
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
System.out.println(date);
The output I get for your date offset to UTC:
Thu Jan 30 12:48:25 UTC 2014
You can provide a "source timezone" to an instance of SimpleDateFormat and the to-be-parsed date string is then converted to your local/default timezone.
TimeZone timeZone = TimeZone.getTimeZone("America/New_York")
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
sdf.setTimeZone(getTimeZone(source));
Be careful when providing the time zone name. TimeZone will silently fail over to GMT if you pass in a string it does not understand as a timezone.
Just to complete previous answers. The same funcionality with Joda-Time:
DateTime dateTime = DateTime.parse("2014-01-30 07:48:25", DateTimeFormat
.forPattern("yyyy-MM-dd HH:mm:ss")
.withZone(DateTimeZone.forID("America/New_York")));
System.out.println(dateTime);
System.out.println(dateTime.withZone(DateTimeZone.UTC));
System.out.println(dateTime.withZone(DateTimeZone.forID("Europe/Madrid")));
---
2014-01-30T07:48:25.000-05:00
2014-01-30T12:48:25.000Z
2014-01-30T13:48:25.000+01:00