Why is this Java Calendar comparison bad?

Question

I'm having an inexplicable problem with the Java Calendar class when I'm trying to compare to dates. I'm trying to compare to Calendars and determine if their difference is > than 1 day, and do things bases on that difference or not. But it doesn't work.

If I do this with the two dates:

    String currDate = aCurrentUTCCalendar.getTime().toString();
    String localDate = aLocalCalendar.getTime().toString();

I get these results:

    currDate  = "Thu Jan 06 05:58:00 MST 2010"
    localDate = "Tue Jan 05 00:02:00 MST 2010"

This is correct.

But if I do this:

    long curr = aCurrentUTCCalendar.getTime().getTime();
    long local = aLocalCalendar.getTime().getTime();

I get these results: ( in milliseconds since the epoch )

    curr  = -125566110120000 
    local =  1262674920000 

Since there is only about a 30 hour different between the two, the magnitudes are vastly different, not to mention that annoying negative sign.

This causes problems if I do this:

long day = 60 * 60 * 24 * 1000; // 86400000 millis, one day

if( local - curr > day )
{
    // do something
}

What's wrong? Why are the getTime().toString() calls correct, but the getTime().getTime() calls are vastly different?

I'm using jdk 1.6_06 on WinXP. I can't upgrade the JDK for various reasons.

Answer 1

Your currDate is "B.C.E. 2010-01-06" (Before Common Era), which is 4019 (2x2010 - 1) years ago.

Try this:

public class StrangeDate {

  public static void main(String[] args) {
    Date d = new Date(-125566110120000L);
    System.out.println(d.toString());
    //prints 'Thu Jan 06 13:58:00 CET 2010' in my locale

    Calendar c = Calendar.getInstance();
    c.setTime(d);
    c.add(Calendar.YEAR, 4019);

    System.out.println(c.getTime().toString());
    //prints 'Wed Jan 06 13:58:00 CET 2010' in my locale
  }

}

The question is: what did you do to get this aCurrentUTCCalendar?