The part timers vacation pay dates back to when UPS had 4/8ers. They were guaranteed 4 hrs a day. If they worked over 4 hrs, then they were guaranteed 8 hrs.
Under our supplement, part timers are guaranteed 20 hrs of pay or 1/52 of the previous calender year's gross pay - which ever is greater.
The same applies to full timers. 40 hrs or 1/52 of the previous year's gross.