Headed west over the Pacific pond I have a similar experience to heading East to Europe (though with several sleep periods for maybe 7ish hours total on the flight). First day there I suddenly get crazy tired about 3p and suffer through dinner and the early evening, but then get back on track pretty quickly. However coming home from Asia for me is brutal, despite sleeping on the plane for a bit. I will wake up at 3-4a the first night and instantly KNOW that I will not be getting back to sleep. That middle of the night wake up shifts for me by ~1 hour each night for the next several nights (so 4-5a, then 5-6a, etc...). And by the time I wake up at my normal time of ~7-7:30a I have lost so much sleep that It still takes a couple more nights to get fully rested. Basically the better part of a week.