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.
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 need to convert local time at a specific city to UTC.
For example ,
convert time in NYC to UTC .
If I pass the local time and country , the service should be able to return the UTC
Is there any library/utility which maps the city/country to timezone and then converts it to UTC ?
I am trying to avoid building a time zone master and do the conversion .
Since this is common problem, if there are any libraries which are already doing it - please revert back
Just need to use Calendar and TimeZone classes?
Define a TimeZone for UTC:
TimeZone tz = TimeZone.getTimeZone("UTC");
And then create the calendar
Calendar cal = Calendar.getInstance(tz);
To retrieve the Date object use calendar.getTime
cal.getTime()
If you already have your date in a Date object (localDate) you can use a formatter:
SimpleDateFormat formatter = new SimpleDateFormat(); formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateinUTC = formatter.format(localDate)
I have done this for my Calendar instance to return Date in UTC timezone:
SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:SS Z");
TimeZone tz = TimeZoneUtil.getTimeZone(StringPool.UTC);
formatter.setTimeZone(tz);
Date dtStart = null;
Date dtEnd = null;
try{
dtStart = formatter.parse(formatter.format(startDate.getTime()));
dtEnd = formatter.parse(formatter.format(endDate.getTime()));
}catch (Exception e) {
e.getStackTrace();
}
It works fine till I format calendar timestamp to return a string date with required timezone but when I parse that string date to Date date, it again picks up local timezone?
I need to store Date object in UTC timezone.
Any help will be highly appreciated!
You can use this:
Date localTime = new Date();
//creating DateFormat for converting time from local timezone to GMT
DateFormat converter = new SimpleDateFormat("dd/MM/yyyy:HH:mm:ss");
//getting GMT timezone, you can get any timezone e.g. UTC
converter.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println("local time : " + localTime);;
System.out.println("time in GMT : " + converter.format(localTime));
It will give:
local time: Fri Jun 21 11:55:00 UTC 2013
time in GMT : 21/06/2013:11:55:00
I hope it will help.
Cheers.
Date object in java will always store the values in the host machine (your system) time zone information.
This is from javadoc :
Although the Date class is intended to reflect coordinated universal time (UTC), it may not do so exactly, depending on the host environment of the Java Virtual Machine.
You should trying using Joda Time which is much advanced.
Instead of setting TimeZone in multiple places, it is a good idea to set timezone using -Duser.timezone=GMT or PST.
And, you can easily test how Java deals with timezone and getTime() ignores timezone with an actual example:
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ"); // print with timezone
TimeZone timeZone = TimeZone.getTimeZone(ZoneId.of("GMT"));
TimeZone.setDefault(timeZone); // set system timezone as GMT
sdf.setTimeZone(timeZone); // formatter also has a timezone
Date date = new Date();
System.out.println(date); // system says GMT date
System.out.println(date.getTime()); // only prints time in milliseconds after January 1, 1970 00:00:00 GMT
System.out.println(sdf.format(date));
timeZone = TimeZone.getTimeZone(ZoneId.of("America/Los_Angeles"));
TimeZone.setDefault(timeZone); // set system timezone as GMT
sdf.setTimeZone(timeZone); // formatter also has a timezone
date = new Date();
System.out.println(date);
System.out.println(date.getTime()); // prints the same value as above, "not including timezone offset"
System.out.println(sdf.format(date));
// GMT and PDT times are same as getTime() only returns time in ms since UTC for the day ignoring timezone which is mostly used for formatting
Wed Mar 14 22:43:43 GMT 2018
1521067423108
2018-03-14T22:43:43+0000
Wed Mar 14 15:43:43 PDT 2018
1521067423125 // not includes timezone in getTime()
2018-03-14T15:43:43-0700 // formatting looks fine
The good explanation of why Date object taking Current time zone value ,
please refer this SO answer
EDIT.
here I am gonna add some important part of that answers.
java.util.Date is 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 have a date as long value, I want to display the Date format in words depends upon the country time zone. Please help me in converting this.
Take a look at the java.text.DateFormat class. It provides several option how to output the current Data and Time.
For example the following code prints the current date and time in the long format option for the en_UK locale:
DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, Locale.UK).format(new Date());
Prints:
23 January 2012 08:17:36 CET
To display any date, just pass the long value to the constructor of the Date object.
DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, Locale.UK).format(new Date(<your long value here>));
I have a date as long value
You need to understand date as long value is the absolute value (UTC) of time in milli seconds since Epoch i.e. '1st Jan 1970 00:00:00'. This value has no timezone information embedded in it. Now if you want to display this time in your current local timezone then simply do this:
Date dt = new Date(1327303085000l);
System.out.printf("Date: %s%n", dt);
It prints:
Date: Mon Jan 23 02:18:05 EST 2012
Note the when it prints the date it automatically prints it with my current timezone.
However if you want customized formattng to display your date then you can take a look at the DateFormat class in Java.