Flight Timezone Calculator

A flight time zone calculator tells you what the clock will show at your destination when you land. The plane does not care about time zones, but the world does: when it is 10:00 in London it is 05:00 in New York, so a seven hour flight that leaves London at 10:00 does not land at 17:00 local time in New York. It lands at about noon. This calculator combines three things: the time you leave, how long you are in the air, and the difference between the two clocks.

You can type the flight duration and the time difference yourself, or search for the From and To places on the map. The map finds the time zone of each place, works out the difference for your departure date (daylight saving time included), measures the great-circle distance and estimates the flight time from that distance.

• Time zone: a region that keeps the same standard time. Computers use names such as Europe/London or Asia/Tokyo (IANA time zones).
• UTC offset: how far a time zone is ahead of (+) or behind (-) Coordinated Universal Time. India is +5:30, Tokyo is +9.
• Daylight saving time (DST): the one hour clock change that many countries make in spring and autumn. It changes the offset, so the time difference between two cities can change during the year.
• Great-circle distance: the shortest distance between two points on the Earth's surface. Flight paths follow it, which is why they look curved on a flat map.

1. Take the departure time on the clock of the departure city.
2. Add the flight duration. This gives the arrival time on the clock of the departure city.
3. Add the time difference (destination offset minus departure offset). It is positive when you fly east and negative when you fly west.
4. The result is the local arrival time at the destination. If it passes midnight, the date moves forward or back by one day.

When you pick places on the map, the flight time is estimated from the great-circle distance. The estimate assumes a cruising speed of about 850 km/h plus 25 minutes for taxiing, take-off, climb and landing. Real flights differ because of wind, routing, air traffic control and aircraft type, so treat the estimate as a guide and use the duration on your ticket when you have it.

• London to New York in January: the offsets are 0 and -5, so the difference is -5 hours. The distance is about 5,570 km, so the estimate is 5,570 ÷ 850 = 6.55 hours = 393 minutes, plus 25 minutes, which is 418 minutes or 6 h 58 min. Leave London at 10:00: 10:00 + 6:58 = 16:58 London time = 11:58 in New York.
• Delhi to Dubai: India is UTC+5:30 and Dubai is UTC+4, so the difference is -1.5 hours. The distance is about 2,205 km, which gives roughly 3 h 01 min. Leave Delhi at 14:00: 14:00 + 3:01 = 17:01 Delhi time = 15:31 in Dubai.
• Sydney to Los Angeles in July: Sydney is UTC+10 and Los Angeles is UTC-7 (daylight saving), so the difference is -17 hours. The distance is about 12,070 km, which gives roughly 14 h 37 min. Leave Sydney at 10:00: 10:00 + 14:37 = 00:37 the next day in Sydney. Subtract 17 hours and you get 07:37 on the day you left, so you land before you took off on the clock.
• London to Tokyo in July: UTC+1 and UTC+9, a difference of +8 hours. The distance is about 9,560 km, roughly 11 h 40 min in the air.

The United States moves its clocks on the second Sunday of March and the first Sunday of November. The United Kingdom and the European Union move theirs on the last Sunday of March and the last Sunday of October. In between, the gap between London and New York is 4 hours instead of 5. That is why this calculator looks up the offsets for your departure date and does not use a fixed number.

Jet lag happens when your body clock is out of step with local time. Most travellers find that flying east, which shortens the day, feels harder than flying west. The recovery estimate in this calculator is a simple rule of thumb of one day for every two hours of time difference. Real recovery depends on the person, so use it for planning only.

• Check the departure and arrival times printed on your ticket. Airlines always show them in local time at each airport.
• If you fly east, try to go to bed earlier for a few days before you leave. If you fly west, try to stay up a little later.
• Get daylight at the destination at times that help your body clock shift, and avoid heavy meals and alcohol on the plane.
• Drink water, stand up and walk around on long flights.
• Set your phone and watch to the destination time as soon as you board, so you start adjusting early.
• Add a margin when you plan a meeting or a pick-up after landing. Delays and immigration queues are not part of the flight time.