Date Computaion in java

Question

The date format iam using is "MM/dd/yy" I want to perform a operation like This:

LastActDate = Todaysdate -(PrchaseDate + 1)

In myDb the date is stored as 2011-07-08 19:30:06(java util date

What's stopping you from performing the operation? What code do you have? What errors are you getting? — S.Lott, Oct 20 '11 at 10:15
possible duplicate of [How to add days to a date in Java](http://stackoverflow.com/questions/2507377/how-to-add-days-to-a-date-in-java) — Don Roby, Oct 20 '11 at 10:22

Saul · Answer 1 · 2011-10-20T10:29:39.910

Use Calendar.add(int field, int amount)

Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules.

import java.util.GregorianCalendar;
import java.util.Calendar;

class AddDates {
    public static void main(String[] args) {

        Calendar today = new GregorianCalendar();
        Calendar purchased = new GregorianCalendar();

        purchased.add(Calendar.DAY_OF_MONTH, 1);

        Calendar lastActDate = new GregorianCalendar();
        lastActDate.setTimeInMillis(today.getTimeInMillis() - purchased.getTimeInMillis());
    }
}

score 1 · Answer 2 · answered Oct 20 '11 at 10:31

1

I highly recommend using joda library for any date/time calculations.

You can do the kind of work you want to do above with it very easily just take a look at examples on the site.

answered Oct 20 '11 at 10:31

Ashkan Aryan

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score 0 · Answer 3 · answered Oct 20 '11 at 10:22

This should work. Assuming the +1 is "plus one day".

try {
    String dateString = "10/20/11";

    SimpleDateFormat df = new SimpleDateFormat("MM/dd/yy");
    Date dt = df.parse(dateString);

    final long ONE_DAY = 1000 * 60 * 60 * 24;      
    Date lastActDate = new Date(System.currentTimeMillis() - (dt.getTime() + ONE_DAY));

    String lastActDateString = df.format(lastActDate);
}
catch ( ParseException pe ) {
    pe.printStackTrace();
}

You should always use a Calendar for date calculations in java. — Stephan, Oct 20 '11 at 11:02

Date Computaion in java

3 Answers3