Jet lag from San Francisco to Hong Kong: what to expect
Fly San Francisco to Hong Kong and local time runs 8 hours behind your body. Land at 17:05 and your body still thinks it's 01:05 in San Francisco. That's the middle of your body's night. At 23:00 in Hong Kong, 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 San Francisco to Hong Kong?
Unaided, westward shifts settle somewhat faster than a day per time zone: about 6 days for this one. S6 S7
This plan targets 5 days.
That's what the plan aims at, not a promise — bodies vary.
For this trip that's 1 day sooner than the unaided estimate, on the effort level that fits around a working day.
On night one the plan's bedtime is 18:35, early by Hong Kong's clock, and it moves later night by night, reaching 23:00 by night 6.
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 San Francisco to Hong Kong flight?
- Departs
- 11:00 San Francisco time
- Lands
- 17:05 Hong Kong time +1 day
- In the air
- about 14h 05m (estimate)
- Light, landing day
- 17:35–18:35 Seek bright light (delay shift)
- Last caffeine, landing day
- 10:30 on the plane
- Last caffeine, first full day
- 13:00
- First night's sleep
- 18:35–01:10
Westbound flights often go by day, so this example leaves San Francisco at 11:00 and lands in Hong Kong at 17:05 in the evening, after about 14h 05m 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.
You cross the date line, and it costs you a calendar day: leave on a Wednesday, land on Thursday, though the flight itself is under 15 hours.
In July the gap is 9 hours, not 8, because San Francisco moves its clocks for summer and Hong Kong doesn't.
On board, the plan keeps you awake apart from a short nap at 05:00 Hong Kong time, saving the real sleep for the night in Hong Kong.
The day before you fly, the plan keeps your morning dim, 07:00–09:00 San Francisco time, and the sun is up in San Francisco by about 07:21 in January, so plan on sunglasses for the commute.
On landing day your last coffee comes on the plane, at 10:30 Hong Kong time, and the plan has none between landing and your first night's sleep. From 01:10, when you wake from that first sleep, it allows it again, until 13:00.
The sun sets in Hong Kong at about 18:04 in January, partway through the 17:35 light step on landing day, so start it outside.
What helps after flying west to Hong Kong?
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 Hong Kong?
Hong Kong to San Francisco is the same 8 hours the other way, eastward. It's the harder direction: about 8 days unaided, and the plan targets 6. Plan the flight home from Hong Kong with your own times.
More routes from San Francisco
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.