Java Answers Forum - Adding/subtracting dates

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Adding/subtracting dates

1 reply on 1 page. Most recent reply: Apr 18, 2007 6:16 AM by Dave H

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Vickie Martin

Posts: 2
Nickname: jasmine14
Registered: Apr, 2004

Adding/subtracting dates

Posted: Apr 17, 2007 6:41 AM

The following code is adding 5 hours to the resultant time. I need to be able to add/substract dates, and it just isn't working right. Any ideas?

long msecSum = 0 ;
DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss.SSS") ;

try
{
Date date1 = dateFormat.parse("01:02:05.101") ;
Date date2 = dateFormat.parse("02:03:10.102") ;
System.out.println("Date1: " + dateFormat.format(date1));
System.out.println("Date2: " + dateFormat.format(date2));
msecSum = date1.getTime() + date2.getTime() ; // adds 5 hours !!!
System.out.println("Sum: " + dateFormat.format(msecSum)) ;
}
catch (Exception e)
{
System.out.println("Unable to process time values");
}

Results:
Date1: 01:02:05.101
Date2: 02:03:10.102
Sum: 08:05:15.203 // should be 3 hours, not 8

Dave H

Posts: 16
Nickname: slebtack
Registered: Apr, 2007

Re: Adding/subtracting dates

Posted: Apr 18, 2007 6:16 AM

Your local timezone is five hours out from GMT. You're in the USA or Canada, in the east but not on the coast?

You can't add times, any more than you can add places. You can add durations, the length of time between two instants in time, just like you can add distances between places.

The Date class represents instants in time. It does not represent durations.

Try subtracting the Date for midnight on the 1st January 1970 from your dates before adding them, then subtracting it from the answer.

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