ASRS 1704480

We have been on the night shift all week, including an all-night transcontinental flight on Day 2 landing at about XA00. We were showing for the day at about XL00 every day. I don't think either of us have gone to bed prior to about XV00 any day this week. Yesterday, at the end of day 5, we landed at about XP30, had to clear customs, and were restocking the airplane, when we received a brief for a XC45 show the next morning, for a flight. This would have been a 10 hour turn, and a 7 hour 15 minute shift from the start time the day before. We fatigued due to the body clock flip. There needs to be a limit on circadian shifts, especially when they are shifts to the left. A 10 hour turn, and a seven hour shift with the first flight the next day though technically a legal brief, is NOT smart, or safe scheduling. We used the fatigue policy, but there are crews out there that would have felt compelled to accept this brief. The crew should not be the last link in the chain, this situation is easily prevented with scheduling limits. This next destination is one of the higher risk airports we fly to, even with the recent improvements, and the risk control measures in place. Being scheduled to go in there after a 10 hour turn, and a 7 hour circadian shift, with a First Officer on IOE added even more to the risk. It should not have been scheduled. I would like to see the fatigue model for this event (as scheduled). I would also like to share this event with scheduling. I would like to know if this flagged anybody's attention during the scheduling process. We have to get better at eliminating these circadian shifts, before we have a mishap.