At a DC you can work 40+ and still use vacation pay, it just doesn’t count toward OT pay.
If my normal days are tues-fri, I can take Friday off, but work 12hrs OT on Monday. Then I’d get 40hrs regular pay, 10 vacation pay, and 2hrs OT pay.
If I use personal holiday instead it’s 30hrs regular, 10 PH, 12 OT.
I can’t cancel out my vacation pay with OT though because too many people worked the system to get out of working mandatory OT and created their own schedules.