Jet Lag Planner

London to Tokyo Jet Lag: Beat the Hardest Trip You'll Fly

Of all the routes I fly with any regularity, London to Tokyo is the only one I still plan for like it might actually beat me, because a few times it has. Tokyo runs 9 hours ahead of London in winter and 8 in summer (Japan keeps no daylight saving, so the gap moves only when Britain does), the nonstop is around 12 hours in the air, and flying east forces your body clock to do the one thing it genuinely resists: move earlier. It manages that at roughly an hour a day, which set against a 9-hour gap tells you most of what you need to know. The good news is that for a jump this big there's a workaround that feels wrong and works anyway, and most of the plan hangs off it.

Nine hours east sits right at the edge of what a clock will do

Left completely alone, your body clock likes to run a bit longer than 24 hours, which is why stretching a day out and going to bed later (what a westbound trip asks of you) feels easy, and why chopping the day short and sleeping before you're tired feels like a fight. Advancing runs at roughly an hour a day against an hour and a half for delaying, and a 9-hour eastward shift sits past the point where the clinical protocols say the clock often gives up on advancing and delays instead, whatever you intended. That's why this route pays back a proper plan more than almost anywhere else you can fly. Left to sort itself out it clears at about a day per time zone, so budget 8 or 9 days, and know that most of what shortens that is how well you handle light in the first few. The mechanics, if you want them, are in Why Flying East Is Harder Than Flying West.

On the plane, start living on Tokyo time

The flight out usually leaves in the London daytime, which hands you a decision about when to sleep. Sleep on Tokyo time, not London time. In practice that means resisting the doze after lunch and saving your real sleep for the back half of the flight, when it's night in Tokyo, so you step off already leaning the right way instead of starting the fight from scratch at the gate.

Don't chase the first Tokyo sunrise

You'll most likely land mid-morning, sun up, the city looking wonderful, and every instinct says march straight out into it. Don't, and this holds whichever of the two strategies below you pick. Do the arithmetic: if you normally wake at 7am in London, your low point is near 4am London time, which is 1pm in Tokyo. So the entire Tokyo morning falls before your low point, and bright light there pushes your clock later, the exact wrong direction if you're trying to advance. Sunglasses on the moment you're out of the terminal, and don't take the first real daylight until the early afternoon. It has to be genuine outdoor light when you do, because a lit room barely registers to the part of your brain that sets the clock. The mechanism is in Morning Light or Evening Light: Which Way You Shift Your Clock.

Then pick one of two routes, and don't mix them

From that point the two strategies part company, and the mistake is doing half of each.

Advance (the short way). Take your light from the early afternoon on day one, then slide that window earlier each day as your low point comes round with you, and keep the evenings dim. It's the direct route, it's uphill the whole way, and it wants a pre-trip head start to have any real chance, because that's what pulls your low point far enough forward that the Tokyo morning stops working against you.

Delay (the long way round). Treat Tokyo as though it were 15 hours west: take bright light in the evening, keep your mornings firmly dark, and push your bedtime later each night until your clock wraps round to Tokyo time from the far side. It sounds backwards. It runs with your body rather than against it, and the clinical protocols note that on eastward flights of eight zones or more the clock often ends up delaying anyway, so you may as well steer it. The condition is that it needs several days to pay off, so it suits a real stay rather than a flying visit.

Either can get you there on a trip of a week or so, and the planner picks based on your actual dates. There's more on the method in Shifting the Long Way Round for Big Eastward Trips.

Coffee at breakfast, then leave it

A coffee at your new Tokyo wake time helps stamp in the morning, so have it and enjoy it. The catch is that caffeine hangs around in your system for hours: in the controlled study everyone cites, 400mg (two to three cups) taken a full six hours before bed still cost people more than an hour of measured sleep, the sort of theft you don't feel until you're staring at the ceiling at 2am wondering what went wrong. Make it a morning drink on this route and cut it off 6 to 9 hours before you plan to sleep.

The trip home is the gentle one

Tokyo to London is the leg you don't need to dread. It's westward, a 9-hour (or 8-hour) delay, and delay is the direction your body takes willingly. These flights tend to land in London in the afternoon or evening, so the whole job is to stay up to a normal local bedtime, get some afternoon light, and accept that you'll wake early for the first few mornings. If you're wondering which direction hurts more, it isn't close: London to Tokyo is far and away the harder half, because that's the one that asks your clock to advance.

Fun fact

For decades airlines couldn't fly the straight line from Europe to Japan, because the direct track runs right over the Soviet Union and that airspace was firmly shut. So London to Tokyo flights went the long way over the North Pole and put down to refuel in Anchorage, Alaska. What's a single long hop today was once a polar crossing with a fuel stop in the snow.

How the Jet Lag Planner handles this

The Jet Lag Planner already treats this as the 9-hour eastward beast it is: it works out whether to advance you or send you the long way round, animates your flight across daylight and dark so the plan makes sense, then hands you day-by-day "get light now" and "avoid light now" windows built around your body's low point, with your coffee cutoff marked. It sticks to the things you actually control, which are light, sleep and caffeine timing, and leaves melatonin and other supplements to you and your doctor. You can plan the exact trip at jetlagplanner.app/plan?from=LHR&to=HND.

Sources

General wellness information, not medical advice. Talk to a clinician before changing your schedule if you have a sleep or health condition.

Last reviewed August 4, 2026.

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General wellness information, not medical advice. Talk to a clinician before changing your schedule if you have a sleep or health condition. © 2026 XOR Limited.