Java- Set time zone with values as UTC-1 to UTC-12 and UTC+1 to UTC+12

Question

I'm converting timezone with values as UTC-1,...,UTC-12, however while printing it date/time it's not displaying converted time zone.

final DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss z");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC-1"));
System.out.println(dateFormat.format(actualDate)); // actualDate showing older time zone and not according to UTC-1

Instead of using UTC-1,UTC-2...and so on, if i use "America/New_York", it shows correct timezone.

final DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss z");
    dateFormat.setTimeZone(TimeZone.getTimeZone("America/New_York"));
    System.out.println(dateFormat.format(actualDate)); // actualDate showing updated time zone EDT

Please suggest if i'm missing something, as I wanted to use values as UTC-1, UTC-2,...UTC+1 and so on.

https://stackoverflow.com/questions/49451976/simpledateformat-settimezone-not-working — Shrey Garg, Dec 30 '19 at 05:12
Thank for pointing to post. However even if i use Calendar, it's behaving same. final Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC-1")); calendar.setTime(actualDate); — Tab, Dec 30 '19 at 05:26

score 4 · Accepted Answer · edited Jun 20 '20 at 09:12

TL;DR: To support "UTC" prefix, use ZoneId. See end of answer.

If you read the documentation, i.e. the javadoc of TimeZone.getTimeZone(String ID), it says:

Gets the TimeZone for the given ID.

Parameters:
ID - the ID for a TimeZone, either an abbreviation such as "PST", a full name such as "America/Los_Angeles", or a custom ID such as "GMT-8:00". Note that the support of abbreviations is for JDK 1.1.x compatibility only and full names should be used.

Returns:
the specified TimeZone, or the GMT zone if the given ID cannot be understood.

So lets test that:

System.out.println(TimeZone.getTimeZone("UTC-1"));

Output

sun.util.calendar.ZoneInfo[id="GMT",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]

The javadoc did say that GMT-8:00 is valid, so lets test that:

System.out.println(TimeZone.getTimeZone("GMT-1"));

Output

sun.util.calendar.ZoneInfo[id="GMT-01:00",offset=-3600000,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]

If you read the javadoc of TimeZone itself:

If the time zone you want is not represented by one of the supported IDs, then a custom time zone ID can be specified to produce a TimeZone. The syntax of a custom time zone ID is:
 CustomID:
         GMT Sign Hours : Minutes
         GMT Sign Hours Minutes
         GMT Sign Hours
 Sign: one of
         + -
 Hours:
         Digit
         Digit Digit
 Minutes:
         Digit Digit
 Digit: one of
         0 1 2 3 4 5 6 7 8 9

As you can see, custom time zones must start with GMT.

The new Java 8 Time API supports UTC-1, e.g.

System.out.println(ZoneId.of("UTC-1"));

Output

UTC-01:00

Which means that if your actualDate value is a java.util.Date, then you can format it like this:

Date actualDate = new Date();
System.out.println(actualDate);

DateTimeFormatter dateFormat = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss z")
                                                .withZone(ZoneId.of("UTC-1"));
System.out.println(dateFormat.format(actualDate.toInstant()));

Output

Mon Dec 30 02:29:41 EST 2019
2019-12-30 06:29:41 UTC-01:00

As you can see, the time was adjusted to the UTC-01:00 time zone.

Thanks, your last end of answer helps, it solves my problem. — Tab, Dec 30 '19 at 08:43

Java- Set time zone with values as UTC-1 to UTC-12 and UTC+1 to UTC+12

1 Answers1