about subtract dates

[mohamed abdo]

how can i subtract two dates from each other,i need the result with the days count between them , (date - date = xxx day)

[Maneesh Godbole]

Moving to a more suitable forum.

[Maneesh Godbole]

Check out Calendar#DAY_OF_YEAR and Calendar#get()

[mohamed abdo]

thank you sir , i found it

     Calendar cal1 = Calendar.getInstance();
       Calendar cal2 = Calendar.getInstance();
        
      // Set the date for both of the calendar instance
       cal1.set(yy,mm,dd);
        cal2.set(yy,mm,dd);
 
       // Get the represented date in milliseconds
       long milis1 = cal1.getTimeInMillis();
        long milis2 = cal2.getTimeInMillis();
         
        // Calculate difference in milliseconds
       long diff = milis2 - milis1;
         
        // Calculate difference in seconds
        long diffSeconds = diff / 1000;
         
       // Calculate difference in minutes
        long diffMinutes = diff / (60 * 1000);
         
       // Calculate difference in hours
        long diffHours = diff / (60 * 60 * 1000);
        
       long diffDays = diff / (24 * 60 * 60 * 1000);  

[Rob Spoor]

That's the naive approach, which is broken because of daylight savings - there are two days a year that are not 24 hours.

The right approach indeed uses Calendar.get() in combination with both Calendar.DAY_OF_YEAR and Calendar.YEAR. In short:
- subtract the day of year of the first date from the day of year of the second date
- add the number of days for each year in difference as well; use Calendar.getActualMaximum(Calendar.DAY_OF_YEAR) to determine how many days a year has.

To make it easier, you can swap the operands if the first date is larger than the second:

public int subtract(Calendar cal1, Calendar cal2)
{
    if (cal1.compareTo(cal2) > 0)
    {
        return -subtract(cal2, cal1);
    }
    // cal1 <= cal2 at this time
    ...
}