CODEWITHSUNDEEP
javadatetimezone
anujprashar
anujprashar

Reputation: 6335

Date from ZonedDateTime instant not in utc

I am creating date like this:

ZonedDateTime now = ZonedDateTime.now(ZoneOffset.UTC);
Date.from(now.toInstant());

I need Date object have current time in utc, but when I print date it gives me my local time and not utc time. I also tried with:

 OffsetDateTime now = OffsetDateTime.now(ZoneOffset.UTC);
 Date date = Date.from(now.toInstant());

But when I print Date again time is not in utc. Am I doing something wrong when creating Date object. Why above 2 approaches not give me Date that have current time in utc.

Upvotes: 0

Views: 1141

Answers (1)

Anonymous
Anonymous

Reputation: 86281

Two points:

  1. Avoid the long outdated Date class, in particular when you are already using classes from java.time, the modern Java date and time API.
  2. A Date object hasn’t got and cannot have a time zone in it.

To print offset or time zone

If you need your offset, you need to hold on to your OffsetDateTime (or ZonedDateTime) object:

    OffsetDateTime now = OffsetDateTime.now(ZoneOffset.UTC);
    System.out.println(now);

On my computer this just printed

2017-11-21T11:53:11.519Z

The Z in the end indicates Zulu time zone, another name for UTC (you may also informally think of it as Zero offset from UTC).

If you would like a more human-readable format, you are right, use a formatter:

    DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL);
    ZonedDateTime now = ZonedDateTime.now(ZoneOffset.UTC);
    System.out.println(now.format(formatter));

Depending on your locale and the time, this prints something like

Tuesday, November 21, 2017 11:53:11 AM Z

Again the Z means Zulu time zone, UTC.

Date is not going to help you

A Date is just a point in time. So is the Instant that you use for initializing the date. None of them has got a time zone or offset. The difference here is their toString methods: The Instant is always printed in UTC, the Date usually (always?) in the JVM’s default time zone. The latter confuses many into thinking the Date has a time zone when it hasn’t. See All about java.util.Date.

As I have demonstrated, a formatter may put a time zone or offset into a string when formatting the date-time. This does not in any way modify the date-time object, whether OffsetDateTime, ZonedDateTime, Instant or Date. The long outdated DateFormat class may do the same when formatting a Date. It cannot and will not set a time zone in the Date object since (and I repeat) a Date object cannot have a time zone in it.

Long story short, you have no need for the outdated Date class that I can see.

Upvotes: 3

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