Jet lag from London to San Francisco: what to expect
Fly London to San Francisco and local time runs 8 hours behind your body. Land at 14:00 and your body still thinks it's 22:00 in London. That's the middle of your body's night. At 23:00 in San Francisco, it's 07:00 for you.
That's a westward shift: your clock has to move later, which is the way it drifts on its own S1. Expect to be sleepy early in the evening for the first few days, and awake before your alarm S1.
How long does jet lag last from London to San Francisco?
Unaided, westward shifts settle somewhat faster than a day per time zone: about 6 days for this one. S6 S7
This plan targets 4 days.
That's what the plan aims at, not a promise — bodies vary.
For this trip that's 2 days sooner than the unaided estimate, on the effort level that fits around a working day.
On night one the plan's bedtime is 21:00, early by San Francisco's clock. It holds there for 4 nights, then moves to 23:00 by night 5.
Studies of aircrew point the same way: after large shifts, westward adaptation runs roughly 50% faster than eastward S6 S8. This trip is on the quick side of that.
What does the plan say for a typical London to San Francisco flight?
- Departs
- 11:00 London time
- Lands
- 14:00 San Francisco time
- In the air
- about 11h (estimate)
- Light, landing day
- 18:40–19:40 Seek bright light (delay shift)
- Last caffeine, landing day
- 13:00 on the plane
- Last caffeine, first full day
- 13:00
- First night's sleep
- 21:00–05:30
Westbound flights often go by day, so this example leaves London at 11:00 and lands in San Francisco at 14:00 in the afternoon, after about 11h in the air.
The flight time is our estimate for a nonstop from the distance, and the trip is set in January. It's the default traveler from the calculator: usually asleep 23:00 to 07:00, no melatonin, Real Life effort.
On board, the plan keeps you awake apart from a short nap at 05:00 San Francisco time, saving the real sleep for the night in San Francisco.
The day before you fly, the plan keeps your morning dim, 07:00–09:00 London time, and the sun is up in London by about 07:57 in January, so plan on sunglasses for the commute.
On landing day your last coffee comes on the plane, at 13:00 San Francisco time, and the plan has none between landing and your first night's sleep. From 05:30, when you wake from that first sleep, it allows it again, until 13:00.
January days are short in San Francisco: about 10 hours of daylight. In January the sun sets in San Francisco at about 17:18, so the 18:40 light step on landing day comes after dark. It has to be bright indoor light.
What helps after flying west to San Francisco?
Going west, you want light before your body's low point, which usually means bright light in the evening and staying up a little later S1. Bright light first thing in the morning works against you. East vs west explains why this direction is the easier one.
On a shift this size, starting before you fly pays off. The Frontiers review describes moving bedtime 30 to 60 minutes later each day for 3 to 4 days before a westward trip S1. The plan's version is one night: bed at 00:00 the night before you fly, an hour later than usual.
And the flight home from San Francisco?
San Francisco to London is the same 8 hours the other way, eastward. It's the harder direction: about 8 days unaided, and the plan targets 6. Jet lag from San Francisco to London has the details.
More routes from London
Sources
Numbered from the site-wide source registry — every Delagged page uses the same numbering.
- S1 Roach GD, Sargent C. Interventions to Minimize Jet Lag After Westward and Eastward Flight. Frontiers in Physiology, 2019;10:927. doi:10.3389/fphys.2019.00927
- S6 Waterhouse J, Reilly T, Atkinson G, Edwards B. Jet lag: trends and coping strategies. The Lancet, 2007;369:1117–29. doi:10.1016/S0140-6736(07)60529-7
- S7 Eastman CI, Burgess HJ. How to travel the world without jet lag. Sleep Medicine Clinics, 2009;4:241–55. doi:10.1016/j.jsmc.2009.02.006
- S8 Samel A, et al. Aircrew adaptation after transmeridian flights, 1995. As cited in Waterhouse et al., The Lancet 2007 (S6). Full text Cited via S6.