Here are 2 examples of adding 30 days to a date
FileDate = '2008/01/30'
parse var FileDate yyyy '/' mm '/' dd
say FileDate '+30=' date('S',date('B',yyyy||mm||dd,'S')+30,'B')
/* OR */
StndDate = yyyy||mm||dd
BaseDate = date('B',StndDate,'S')
Date#30 = date('S',BaseDate + 30,'B')
say FileDate '+30=' Date#30