When I got to London, it took me two solid weeks to get turned around.I’d taken an overnight flight and lost 5 hours, and I was advised not to sleep the entire first day until it was bed time. So, I was awake all day Thursday, all Thursday night, and all day Friday. To me, when I landed in London, it was 4AM. It was 9AM London time, and I was like a zombie walking through Heathrow. Which is a freakin’ huge airport, BTW. I stayed up all day Friday and went to bed around 9PM, thinking that I’d magically be turned around the next day, but I had trouble. I’d get tired during the day, and then get a second wind when I should have been going to bed. By the time two weeks had passed, I was on a normal GMT sleep schedule.
Coming back home, I had a daytime flight. I gained 5 hours, and when I landed in the states it was 8PM to my body, but 3PM local time. Once again, I made myself stay up until it was time for bed in this time zone, but I had trouble staying asleep. Or I’d wake up an hour before my alarm and get tired during the day. I’d be really tired by nightfall, but I couldn’t sleep through a whole night. It was awful. It took me a solid two weeks to get back on US time.
Everyone is different and will acclimate differently, but I’d say to expect at least a week of confusing exhaustion and sudden alertness. Bodies aren’t designed to go from one time zone to another, so I’d suggest ear plugs so nothing accidental wakes you up, and an eye mask as well. I actually used an eye mask and ear plugs the entire time I studied abroad, since I had two roommates and we were never in bed at the same time. I could go to bed hours before them and not get woken up by the light or noise they were making. It was lovely :)