How to Set Time Zone of a java.util.Date

1. Use ZonedDateTime to Set Time Zone of a java.util.Date
2. Use UTC Instant to Set Time Zone of a java.util.Date

This quick tutorial will look at how to use Java to set the time zone associated with a date. The java.util.Date has no time zone.

It denotes the UTC/GMT standard with no time zone offset. Because when creating a string representation, its toString function uses the JVM’s default time zone as the basis for its application.

The built-in java.util.Date, .Calendar, and java.text.SimpleDateFormat classes are generally difficult to work with and should be avoided. We’ll use the java.time package that comes standard with Java 8 instead.

Below are the ways the java.time classes can represent a time zone.

Use ZonedDateTime to Set Time Zone of a java.util.Date

Applying a time zone, an offset, and the guidelines for dealing with irregularities like Daylight Saving Time or DST is a better option than the alternative.

When a ZoneId is used with an Instant, a ZonedDateTime is produced. Always be sure to use the correct name for the time zone.

Abbreviations of three to four letters, such as EST that are neither specific nor standardized should never be used.

ZoneId zId = ZoneId.of("Pakistan/Karachi");
ZonedDateTime zonedt = ZonedDateTime.ofInstant(instant, zId);

Use UTC Instant to Set Time Zone of a java.util.Date

Instant is the fundamental building component of java.time. It represents an instant on the timeline that is measured in UTC.

Implement the majority of your application logic using Instant objects.

Instant instant = Instant.now();

LocalDateTime

When any text being parsed does not include any indicators of offset or zone, then it should be interpreted as a LocalDateTime.

If you are definite about the time zone that should be used, you may generate a ZonedDateTime by assigning a ZoneId. See the following sample of code.

LocalDateTime.parse("2022-09-10T01:13:15.123456789").atZone(ZoneId.of("Asia/Pakistan"))