ActionScript for Flash MX: The Definitive Guide, 2nd Edition By Colin Moock
Chapter 18. ActionScript Language Reference
Date.setUTCDate( ) Method
Flash 5
assign the day of the month (UTC time)
date.setUTCDate(day)
Arguments
day
An integer from 1 to 31, representing the new day of the month for date in UTC time. If you specify a day greater than the number of days in the current month, it causes the month to increment accordingly. For example, if the current month is 8 (September) and you specify 31 for the new day, it is treated as October 1. The day becomes 1, and the month becomes 9 (October).
Returns
An integer representing the number of milliseconds between the new date and midnight, January 1, 1970, in UTC time.