Jet lag from Hong Kong to London: what to expect
Fly Hong Kong to London and local time runs 8 hours behind your body. Land at 15:15 and your body still thinks it's 23:15 in Hong Kong. That's the middle of your body's night. At 23:00 in London, 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 Hong Kong to London?
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 London'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 Hong Kong to London flight?
- Departs
- 11:00 Hong Kong time
- Lands
- 15:15 London time
- In the air
- about 12h 15m (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 Hong Kong at 11:00 and lands in London at 15:15 in the afternoon, after about 12h 15m 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.
In July the gap is 7 hours, not 8, because London moves its clocks and Hong Kong doesn't.
On board, the plan keeps you awake apart from a short nap at 05:00 London time, saving the real sleep for the night in London.
The day before you fly, the plan keeps your morning dim, 07:00–09:00 Hong Kong time, and the sun is up in Hong Kong by about 07:05 in January, so plan on sunglasses for the commute.
On landing day your last coffee comes on the plane, at 13:00 London 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 London: about 9 hours of daylight. In January the sun sets in London at about 16:27, 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 London?
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 London?
London to Hong Kong 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 London to Hong Kong has the details.
More routes from Hong Kong
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.