compareTo()
Compares the time values represented by two Calendar objects.
Syntax
Numeric compareTo(Calendar other)
            - other is the calendar to compare.
 
Usage
The time value is expressed in millisecond offsets from the Epoch January 1, 1970 00:00:00.000 GMT Gregorian.
This method returns:
0if the time represented by the argument is equal to the time represented by this Calendar.- A value less than 0 if the time of this Calendar is before the time represented by the argument.
 - A value greater than 0 if the time of this Calendar is after the time represented by the argument.