What it is for
Tickets show departure in the origin city's time and arrival in the destination city's time, and doing that math in your head with time zones and daylight saving is easy to get wrong. Enter the departure (local date and time) and the flight duration and this tool returns the local arrival date and time, plus the same moments in UTC.
How the calculation works
The local departure time is converted to UTC using the official IANA time zone of the origin city on that date, with one extra verification pass to settle the days when daylight saving starts or ends. We then add the flight duration, which is the same in every time zone, and convert the resulting instant to the destination's zone. Formula: arrival UTC = departure UTC + duration; local arrival = arrival UTC + destination offset.
Worked example
Departing São Paulo (UTC−3) on 15 July at 22:00 on an 11 h 30 min flight to Lisbon: departure is 01:00 UTC on the 16th, arrival is 12:30 UTC and, since Lisbon is on UTC+1 in the European summer, you land at 13:30 on 16 July. The same flight in December lands at 12:30, because Lisbon is on UTC+0. New York to London rolls over to the next day: leaving at 19:00 in July on a 7 h flight arrives at 07:00 the next day.
The International Date Line
Flights across the Pacific can arrive "before" they left or on an unexpected calendar day. A Sydney to Los Angeles flight leaving at 10:00 in July and lasting 13 hours lands at 06:00 on the same calendar day, for example. The "day relative to departure" line shows +1, 0 or −1 to make this clear.
Limits
The flight duration is something you enter, so the result is only as good as the airline's estimate, and delays are not modeled. If the local departure time falls in the gap that does not exist when clocks spring forward, it is resolved to an adjacent valid instant (one hour off). If a country changes its time zone rules after your browser's tables were published, small differences are possible until the system updates.
Frequently asked questions
Should the flight duration include the time zone difference?
No. Enter the real time in the air, as on your ticket (for example 11 h 30 min). The calculator applies the time zone difference itself.
Is daylight saving time considered?
Yes, at both departure and arrival, using each city's official time zone on the chosen date.
Why can the arrival fall on a different day?
Because the destination's local clock can be many hours ahead of or behind the origin. The day line shows +1, 0 or −1 relative to the departure day.
Can I use it for connecting flights?
Yes: enter the total travel time (flights plus layovers) as the duration, or calculate each leg separately.