Los Angeles to London advances your body clock by about eight hours – a large eastward shift, the hardest kind, usually flown overnight. Most travellers feel strongly jet-lagged for around a week – notably worse than the westbound leg. Sleeping on the plane and getting bright London morning light matter most.
Los Angeles to London at a glance
| Time difference | London is 8 hours ahead of Los Angeles for most of the year |
|---|---|
| Direction | Eastward – your clock advances (the hardest direction) |
| Time zones crossed | About 8 |
| Jet lag estimate | Roughly 7 out of 10 (high – harder than the westbound trip) |
| Body clock on arrival | You land in the London afternoon; your body reads the early hours of the morning |
| Adaptation | Around 7-8 days |
| Flight time | About 10 hours (overnight, eastbound) |
These figures are transparent estimates, not clinically validated. The exact time difference depends on the date; the calculator resolves it for your trip.
Time difference and direction
London is eight hours ahead of Los Angeles for most of the year. You travel east, so your clock must advance – the hardest direction – which makes this return noticeably worse than the outbound London to Los Angeles, even though the shift is the same eight hours. The eastward penalty on an eight-hour advance is exactly the asymmetry described in why does jet lag happen.
Jet lag estimate and body clock
Expect a high jet lag, around seven out of ten. These flights usually leave Los Angeles in the evening and arrive in London in the afternoon a day later, but your body reads the pre-dawn hours on arrival, so you will be fading just as the London day is in full swing. Falling asleep at the London bedtime and waking through the London morning are hard for the first several days.
Adaptation: how long it lasts
Plan for seven to eight days. An eight-hour eastward shift advances only about an hour a day, so this is among the harder mainstream long-hauls. Bright London morning light is the strongest lever, and mistimed light can set you back, so use the light exposure planner.
Before the flight
For the three nights before departure, go to bed and wake an hour earlier each night, and get early-morning light in Los Angeles, to start the advance at home. You cannot fully pre-adapt to eight hours, but a partial head start meaningfully shortens the job in London.
During the flight
This is an overnight eastbound flight, so sleep as much as you can, as early as you can, timed to London’s night. Set your watch to London time on boarding, use an eye mask and earplugs, hydrate, and avoid alcohol. Check the exact rest window with the flight sleep calculator.
After arrival
Because you land in the afternoon, aim to stay up to a normal London bedtime that night, then get bright light the next morning to keep advancing your clock. Avoid bright light late in the evening, skip long daytime naps, and keep meals firmly on London time. Steady repetition over about a week closes an eight-hour eastward gap.
Calculate your personal plan
Get a day-by-day schedule tailored to your exact departure time and sleep habits, with this route already filled in.
Sources
- U.S. Centers for Disease Control and Prevention – CDC Yellow Book, “Jet Lag” chapter – eastward travel harder, morning light for phase advance.
- NHS – “Jet lag” (nhs.uk/conditions/jet-lag/), last reviewed 31 May 2023.
- Eastman CI & Burgess HJ (2009), Sleep Medicine Clinics – phase-advance scheduling for eastward travel.
- IANA Time Zone Database – offsets for America/Los_Angeles and Europe/London.