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Asked: 2026-06-17T06:33:14+00:00

When UTC date is formatted by DateFormat#format() , I expect to get a String

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When UTC date is formatted by DateFormat#format(), I expect to get a String of UTC date formatted, but not.

Please look at the code below. These tests are passed.

My question is why does DateFormat#format() return a time of 12:00 past UTC date? What am I missing here?

Date date(int millisecondsSinceEpoch, bool isUtc) =>
    new Date.fromMillisecondsSinceEpoch(millisecondsSinceEpoch, isUtc:isUtc);

DateFormat df = new DateFormat("yyyy-MM-dd hh:mm");

// JST (+9.00)
expect(date(0, false).toString(), equals("1970-01-01 09:00:00.000"));
expect(df.format(date(0, false)), equals("1970-01-01 09:00"));

expect(date(0, true).toString(), equals("1970-01-01 00:00:00.000Z"));
// Why 12 o'clock?
expect(df.format(date(0, true)), equals("1970-01-01 12:00"));
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1 Answer

  1. Editorial Team

    Your format string you’ve written uses lowercase hh which is a 12 hour clock. Use uppercase HH for the hours to get a 24-hour clock. The output you are getting in the last line is currently saying 12 midnight, rather than 00 hours in a 24-hour clock.

    See the explicit pattern syntax in DateFormat

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