New York → Tokyo

Jet lag is the mismatch between local time in Tokyo and the clock your body is still running from New York. A delay asks your body to become sleepy and wake later, which is often easier than an equivalent advance. JetLagPlan models the shortest useful phase shift rather than blindly treating the printed UTC offset as the amount your body must move. Local clocks are 13 hours apart, but your body does not need to move through that full distance. On a 24-hour circadian clock, the shorter adjustment is 11 hours in the delay direction. A reasonable planning estimate for this route is around 8 days of adjustment, with individual response varying by sleep history, light exposure and schedule.

Late-afternoon and early-evening light supports a delaying plan. During the first recovery days in Tokyo, avoid deliberately seeking very bright light extremely early in the morning, then use normal daylight through the day and stronger late-day light where practical.

If your schedule allows, begin 3 days before departure. Move your normal bedtime and wake time 30–60 minutes later each day and reinforce the change with brighter light later in the day. Partial preparation still helps; do not sacrifice a full night of sleep simply to chase a perfect schedule.

Switch your reference clock to Tokyo time at boarding. Protect destination daytime by staying awake when practical, then sleep during the destination night window. Hydration, movement and lighter meals make it easier to follow that timing without turning the flight into another source of sleep disruption.

For a delaying plan in Tokyo, late-afternoon or early-evening light is useful. Stay awake to a sensible local bedtime, keep any emergency nap short and earlier in the day, and avoid making very early morning bright light your strongest light signal during the first recovery days.