Java Date month difference

Question

I have start date and end date.

I need the number of months between this two dates in Java.

For example

• From date: 2009-01-29
• To date: 2009-02-02

It has one jan date and one Feb date.

It should return 2.

Answer 1

It depends on your definition of a month, but this is what we use:

int iMonths = 0;

Calendar cal1 = GregorianCalendar.getInstance();
cal1.setTime(date1);

Calendar cal2 = GregorianCalendar.getInstance();
cal2.setTime(date2);

while (cal1.after(cal2)){
    cal2.add(Calendar.MONTH, 1);
    iMonths++;
}

if (cal2.get(Calendar.DAY_OF_MONTH) > cal1.get(Calendar.DAY_OF_MONTH)){
            iMonths--;
        }


return iMonths;

Answer 2

below logic will fetch you difference in months

(endCal.get(Calendar.YEAR)*12+endCal.get(Calendar.MONTH))-(startCal.get(Calendar.YEAR)*12+startCal.get(Calendar.MONTH))

Answer 3

Here a complete implementation for monthDiff in java without iterations. It returns the number of full month between two dates. If you want to include the number of incomplete month in the result (as in the initial question), you have to zero out the day, hours, minutes, seconds and millisecondes of the two dates before calling the method, or you could change the method to not compare days, hours, minutes etc.

import java.util.Date;
import java.util.Calendar;
...
public static int monthDiff(Date d1, Date d2) {
    int monthDiff;

    Calendar c1, c2;
    int M1, M2, y1, y2, t1, t2, h1, h2, m1, m2, s1, s2, ms1, ms2;

    c1 = Calendar.getInstance();
    c1.setTime(d1);

    c2 = Calendar.getInstance();
    c2.setTime(d2);

    M1 = c1.get(Calendar.MONTH);
    M2 = c2.get(Calendar.MONTH);
    y1 = c1.get(Calendar.YEAR);
    y2 = c2.get(Calendar.YEAR);
    t1 = c1.get(Calendar.DAY_OF_MONTH);
    t2 = c2.get(Calendar.DAY_OF_MONTH);

    if(M2 < M1) { 
        M2 += 12;
        y2--;
    }

    monthDiff = 12*(y2 - y1) + M2 - M1;

    if(t2 < t1)
        monthDiff --; // not a full month
    else if(t2 == t1) { // perhaps a full month, we have to look into the details
        h1 = c1.get(Calendar.HOUR_OF_DAY);
        h2 = c2.get(Calendar.HOUR_OF_DAY);
        if(h2 < h1)
            monthDiff--; // not a full month
        else if(h2 == h1) { // go deeper
            m1 = c1.get(Calendar.MINUTE);
            m2 = c2.get(Calendar.MINUTE);
            if(m2 < m1) // not a full month
                monthDiff--;
            else if(m2 == m1) { // look deeper
                s1 = c1.get(Calendar.SECOND);
                s2 = c2.get(Calendar.SECOND);
                if(s2 < s1)
                    monthDiff--; // on enleve l'age de mon hamster
                else if(s2 == s1) { 
                    ms1 = c1.get(Calendar.MILLISECOND);
                    ms2 = c2.get(Calendar.MILLISECOND);
                    if(ms2 < ms1)
                        monthDiff--;
                    // else // it's a full month yeah
                }
            }
        }
    }
    return monthDiff;
}