Generating UTC Time in java

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青春惊慌失措
青春惊慌失措 2021-01-19 01:43

I want to get the UTC time for 01/01/2100 in Java to \'2100-01-01 00:00:00\'. I am getting \"2100-01-01 00:08:00\". Any idea, how to correct this.

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2条回答
  •  一个人的身影
    2021-01-19 02:33

    You need to specify the time zone for the SimpleDateFormat as well - currently that's parsing midnight local time which is ending up as 8am UTC.

    TimeZone utc = TimeZone.getTimeZone("UTC");
    Calendar calendar = Calendar.getInstance(utc);
    
    DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
    df.setTimeZone(utc);
    Date finalTime = null;
    
    try
    {
        finalTime = df.parse("01/01/2100");            
    } catch (ParseException e)
    {
        e.printStackTrace();
    }
    
    calendar.setTime(finalTime);
    

    As ever though, I would personally recommend using Joda Time which is far more capable in general. I'd be happy to translate your example into Joda Time if you want.

    Additionally, I see you're returning calendar.getTime() - that's just the same as returning finalTime as soon as you've computed it.

    Finally, just catching a ParseException and carrying on as if it didn't happen is a very bad idea. I'm hoping this is just sample code and it doesn't reflect your real method. Likewise I'm assuming that really you'll be parsing some other text - if you're not, then as Eyal said, you should just call methods on Calendar directly. (Or, again, use Joda Time.)

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