javascript Date setDate( )

Sets the date within the month for an instance of the Date object. If you specify a date beyond the end of the object's current month, the object recalculates the date in the succeeding month. For example, if a Date object is set to December 25, 2002, you can find out the calendar date ten days later with the following construction:

myDate.setDate(myDate.getDate( ) + 10);