Japan Jet Lag Calculator

One useful constant: Tokyo — and with it the Japan clock — stays pinned to UTC+9 for the whole trip. Two Japan specifics compound the shift: Tokyo sits at 40 m (altitude makes poor sleep feel worse), and East Asia sits on the Asia travel circuit most Japan itineraries follow.

Concretely: London → Tokyo = 9 h, New York → Tokyo = 14 h, Tokyo → Tokyo = 0 h, Sydney → Tokyo = 1 h. Reference frame for Japan: Tokyo keeps UTC+9 and sits 40 m above sea level in East Asia, with that same offset in every season.

Dry cabin air quietly drains you on the way to Japan; an extra 500 ml of water per 3 hours in the air keeps the Tokyo arrival day survivable. Before you fly to Japan: move bedtime and meal times 30–60 minutes per day toward Tokyo time for 3–4 days. In the air on the Japan route (arrival UTC+9), hydrate hard and skip alcohol.

Sleep only when it is night in Tokyo, so the cabin previews Japan hours. Morning light is the strongest reset signal Japan offers at this shift size. In Tokyo (UTC+9), get it outdoors before 10am local.

Applied to this East Asia trip: 9 hours east from London to Tokyo maps to about 9 reset days, so a Japan itinerary should front-load outdoor time on days one to 9.

A 10-minute warm shower an hour before bed speeds the core-temperature drop that starts sleep — a real head-start on the first jangled Japan nights in Tokyo. If Japan wakes you at 4am on night one in Tokyo, stay dark and still — checking the clock anchors wakefulness.

Sleep follows light in Japan: book a dark room in Tokyo (40 m), keep it cool (16–20°C), and wear a mask if the early sunrise leaks through the blinds. Practical baseline: lights out in a dark 16–20°C Tokyo room (40 m, UTC+9), and no evening alcohol for the first two nights while the Japan clock settles.