Generating UTC Time in java

Question

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.

public Date getFinalTime() {
    Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

    DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
    Date finalTime = null;

    try
    {
        finalTime = df.parse("01/01/2100");            
    } catch (ParseException e)
    {
        e.printStackTrace();
    }

    calendar.setTime(finalTime);
    return calendar.getTime();
}

Answer 1

You need to set the time zone of the SimpleDateFormat object as well, otherwise it assumes the default time zone.

Anyway, it seems like using only a Calendar is enough in your case. Use its setters to set the right values for all fields (year, month, day, hour, etc), and then retrieve the time.

Answer 2

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.)