Around 15 years ago a study was done by Sheffield University. They looked at ATC Shift patterns and recommended that, over a 10 day cycle, the pattern was MMAANNSOOO. This was adopted by the Unit at which I worked and it replaced a system which used to go AAOMMNNSOO.
The logic of the Sheffield study was that the shifts get later and allow your "body-clock" (circadian rhythm) to adjust gradually to the later hours.
In my opinion, the change was not beneficial and actually made me feel considerably more tired. However, to be fair, it put all the days off together which quite a few seemed to like this and, I suspect, voted for it for that reason. The problem was that you were at your Unit for 7 days on the run and got throughly fed up with it.
I'm rather amazed that someone on this thread mentions doing 0645 to 1400 and returning the same night. That's like the bad old days of the AMNSO "4 Watch" system which prevailed up to something like the mid-70s. By the end of the night duty - which was in those days 12 hours long - you had done 17 hours out of 24 on duty.