Question

import java.util.GregorianCalendar;

public class FullYear {

    public static void main(String[] args) {

        GregorianCalendar cal1 = new GregorianCalendar(2011,2,9); 
        GregorianCalendar cal2 = new GregorianCalendar(2011,2,12); 
        long ms1 = cal1.getTime().getTime(); 
        long ms2 = cal2.getTime().getTime(); 
        long difMs = ms2-ms1; 
        long msPerDay = 1000*60*60*24; 

        System.out.println(difMs);
        System.out.println(msPerDay);

        double days = difMs / msPerDay;

        System.out.println(days);

        GregorianCalendar cal11 = new GregorianCalendar(2011,2,9); 
        GregorianCalendar cal22 = new GregorianCalendar(2011,2,19); 
        long ms11 = cal11.getTime().getTime(); 
        long ms22 = cal22.getTime().getTime(); 
        long difMs1 = ms22-ms11; 
        long msPerDay1 = 1000*60*60*24; 

        System.out.println(difMs1);
        System.out.println(msPerDay1);

        double days2 = difMs1 / msPerDay1;

        System.out.println(days2);

    }

}

This outputs 3.0 and 9.0 (I expect 10!!). This does integer division, so 9.0 is actually 9.95. However, my question is…

• The difference between February 9th and February 19th is 860400000 milliseconds, or 239 hours.
• The difference between February 9th and February 12th is 259200000 milliseconds, or 72 hours.

Shouldn’t the first difference be 240 hours?

Answer 1

You are calculating the differences for March, not February, and you have engulfed the onset of Daylight Saving Time.