the 1st and the 15th
These days in the Army are well known as pay-days. These are also the days (or weekend of) that lower enlisted (privates) spend all of the their money on: Booze, clubbing, and other useless shit.
*partying at the club or local strip club*
Private 1: "Man, I wish I could get out here more."
Private2: "I know, but only the 1st and the 15th."