I used to work 7pm - 7am night shift. 3 days on, 4 days off one week and 4 days on, 3 days off the next. With lots of melatonin, exercise and careful adherence to my bizarre schedule I was able to train my body into a diurnal inversion cyclical sleep schedule. As soon as my 3/4 day work week was over I would -- over the course of one day -- inverter myself back to being awake during the day. When my weekend was over I would invert back to sleeping during the day. I did this for years.
Work day 1: wake up 12pm, sleep 7am
Work day 2: same
Work day 3: same
Day off 1: wake up 12 pm, sleep at 10pm
Day off 2: wake up 8am, sleep 10pm
Day off 3: wake up 8 am, sleep 1am
Day off 4: wake up 12pm, sleep 3am
Repeat.
Melatonin was literally the only way I managed that.