Java Date and Daylight Saving

问题:

I'm trying to print all the hours of the day using a for loop and incrementing a Date object. But I can't have "Sun Mar 25 02:00:00", I only have these:

Sun Mar 25 01:00:00 CET 2012
Sun Mar 25 03:00:00 CEST 2012
Sun Mar 25 03:00:00 CEST 2012
Sun Mar 25 04:00:00 CEST 2012
Sun Mar 25 05:00:00 CEST 2012

I'm not interested in having the TimeZone. I think that the problem is due to the Daylight Saving, but I need the "Sun Mar 25 02:00:00". How can I do to create that date?

回答1:

You probably want a DateFormat object that is set up for UTC (which does not observe daylight savings), using a calendar set to UTC will also simplify things quite a bit.

public static void main(String[] args) {
    TimeZone utc = TimeZone.getTimeZone("UTC");
    Calendar date = Calendar.getInstance(utc);
    DateFormat format = DateFormat.getDateTimeInstance();
    format.setTimeZone(utc);
    date.set(2012, 02, 24, 23, 00, 00);
    for (int i = 0; i < 10; i++) {
        System.out.println(format.format(date.getTime()));
        date.add(Calendar.HOUR_OF_DAY, 1);
    }
}

This provides the following output:

Mar 24, 2012 11:00:00 PM
Mar 25, 2012 12:00:00 AM
Mar 25, 2012 1:00:00 AM
Mar 25, 2012 2:00:00 AM
Mar 25, 2012 3:00:00 AM
Mar 25, 2012 4:00:00 AM
Mar 25, 2012 5:00:00 AM
Mar 25, 2012 6:00:00 AM
Mar 25, 2012 7:00:00 AM
Mar 25, 2012 8:00:00 AM

Of course, you can use the formatter to format your date however you like.

回答2:

The Calendar class allows you to specify a time zone when you convert Date values. See the API doc