In Czech "pásmová nemoc" — what you suffer after crossing several time zones in a short period.

In my case it was six zones. A shift from GMT+1 to GMT-5 and back. To avoid the unwanted side effects: on the outbound journey I decided to push through and not sleep, going to bed only after checking into the hotel (around 23:30). The following days I woke up earlier (around 5-6) but was always rested and fresh. On the way back I flew overnight, which I made use of — immediately after dinner on the plane I fell asleep (around 3.5 hours of sleep), woke up an hour before landing (already in GMT time), and made it through (a nap on the train was unavoidable) without any trouble until the evening when I got home (GMT+1). I have to say that even after two days I don't feel any notable fatigue, headaches, or other issues. It's certainly down to the fairly good timing of the flights (outbound in the evening and returning in the morning — relative to GMT).