4 branches, 3 (not 4) sets of etiquette

The library system where I work has four locations. Here is how changing of the desk shifts "on the hour" works at each one:

Location #1: If you're not arriving to relieve your colleague 5 minutes before the hour, you're late.

Location #2: You arrive on the hour, on the dot, period.

Location #3: You wander in around 5 minutes past the hour. Sometimes the person on desk has to call their replacement to remind them to come out.

Location #4: Half the staff thinks the cultural standard is the same as location #1 and half the staff thinks it's the same as location #3, and they hate each other. You cannot win. If you try the location #2 approach, BOTH groups hate it.