Jet lag is your body clock arguing with the local clock. Shifting your schedule before you fly removes most of the fight. Tell this calculator which way you are going and how many zones you are crossing, and it builds the day-by-day plan.

Why eastward is harder

The human circadian rhythm runs slightly longer than 24 hours, so delaying your clock (flying west, going to bed later) is easier than advancing it (flying east, going to bed earlier). CDC guidance notes that westward adaptation is often faster than eastward adaptation, averaging about 1.5 hours per day westward versus about 1 hour per day eastward. Individual adjustment varies.

Adaptation varies by person and route. The CDC Yellow Book cites average circadian adaptation of about 1 hour per day after eastward travel and about 1.5 hours per day after westward travel. Shifting sleep toward destination time before travel and timing light exposure can help.

Light is the lever, not willpower

• Flying east: seek bright light early in the destination morning; avoid it in the late evening. That pulls your clock earlier.
• Flying west: seek light in the late afternoon and evening; keep mornings dim. That pushes your clock later.
• Get the direction backwards and you make jet lag worse — the wrong-time light exposure shifts you away from local time.
• On the plane: set your watch to destination time when you board and decide whether this is a “sleep” leg or a “stay awake” leg. Skip the alcohol; it fragments the sleep you do get.
• On arrival: local meal times, outdoor daylight, movement, and a firm local bedtime. Naps capped at 30 minutes.

FAQ

How long does jet lag last?

There is no exact recovery formula. The CDC Yellow Book cites average adaptation of roughly 1 hour per day eastward and 1.5 hours per day westward, with substantial individual variation. Timed light and pre-trip schedule shifts can help.

Is it worth shifting my schedule if I only have one day?

Yes, modestly. One day of a 30-to-60-minute shift will not cover an eight-zone flight, but it reduces the gap you have to absorb on arrival, and it forces you to plan the arrival light exposure, which matters more than the pre-shift itself.

Should I take melatonin?

Many travellers use a low dose in the destination evening for eastward flights, but timing determines whether it helps or shifts you the wrong way, and it interacts with some medications. Ask a doctor or pharmacist about dose and timing rather than guessing. This page is not medical advice.

What about short trips?

For a trip of two days or less across a big shift, many people do better staying close to home time: keep meetings and sleep in your home-clock window if the schedule allows, and skip the adaptation entirely.

What travel gear is actually useful?

A comfortable travel pillow, sleep mask and simple noise control are the highest-value basics for most travelers. Add portable white noise only if unfamiliar room noise is a recurring problem.

Pair the timing plan with simple travel-sleep gear

The calculator handles timing. For the flight and hotel itself, our Travel Sleep hub compares current pillows, masks, earplugs, sleep earbuds and portable white-noise options.

Build a travel sleep kit

For overnight layovers, also see How to Sleep in an Airport.