Jet lag flying San Francisco to London
Flying San Francisco → London crosses 8 time zones eastward, so you'll need to advance your body clock (go to bed earlier). That's a severe case, plan for about 8 days to fully adjust. The interactive plan below gives you a day-by-day light and sleep schedule in London time.
Seek bright light in the morning; dim screens and lights in the late evening.
All times in London local time. Move your bedtime toward the top row and let daylight do the rest.
Jet lag on the San Francisco–London route
London runs UTC+1 and San Francisco runs UTC-7, a raw gap of 8 hours. Your body takes the shorter route, so the real task is a 8-hour phase advance, everything needs to happen earlier. Because this is an eastward trip, it lands as a severe case: expect the first 2 days to be the roughest, with full adjustment near day 8.
Why eastward is the hard direction
Flying east compresses your day, you land and it's already later than your body thinks, so you must fall asleep before you're tired. Our internal clock naturally runs a touch longer than 24 hours, which makes going to bed earlier the harder ask. The fix is morning light: bright daylight (or a light box) in the first hours after waking in London pulls your clock earlier, while dim evenings stop it drifting back.
On the plan above, arrival night targets a 07:00 bedtime in London, that's where your body already is, and each day it moves toward a normal 23:00. Follow the sun-and-shade windows and you nudge your clock roughly an hour a day. Adjusting your sleep in the three evenings before you fly (toggle it on) can shave the worst of it off before you even board.
Two practical notes: caffeine helps you stay awake for a westward delay but wrecks an eastward advance if taken late, and a short 20-minute nap on arrival is fine as long as it's before local mid-afternoon. Melatonin timing is the mirror of light, a small dose in the early evening supports an advance, but check with a clinician first.
FAQ
How many time zones between San Francisco and London?
8 zones, travelling eastward. Your body clock has to advance by 8 hours.
How long does jet lag from San Francisco to London last?
Roughly 8 days, the body shifts about one zone per day going eastward, and light exposure at the right times speeds it up.
Is it worse flying east or west?
East is harder. Flying east forces a phase advance (earlier bedtime), which the body resists; flying west is a phase delay (later bedtime), which is easier because our natural clock runs slightly longer than 24 hours.