Prior to this, the rest / duty rules were very simple. Nothing like flight crews.
- 1 day in 7 had to be off duty
- 8 hours between duty periods (split shifts notwithstanding)
- 10 hour max duty day
- Per contract, no more than 2 hours on position without a break
So, for these mid shifts, you could work 3pm-11pm on Monday, 7am-3pm on Tues, and come in that late evening at 11pm, and work until 7am the next morning.
It has exactly 8 hours rest between each, with 8 hour shifts.