Reading flight times when the zones do not match
Your ticket says depart 9pm, arrive 6am. That is not a nine-hour flight — and connections booked on that assumption get missed.
Arrival times are local, always
Every airline publishes departure in the origin's local time and arrival in the destination's local time. Neither figure tells you the flight duration on its own, and subtracting one from the other gives the wrong answer whenever the zones differ.
A worked example
London to Dubai: depart 9:00pm, arrive 7:00am. That looks like ten hours. Dubai is four hours ahead of London in winter, so the actual flight is about six hours. Book a connection assuming ten and you will be sitting in the terminal for four hours.
The reverse is worse. Dubai to London: depart 2:00am, arrive 6:00am. That looks like four hours; it is actually about eight.
The rule
Flight duration = arrival local − departure local + (origin offset − destination offset). Or simply read the duration the airline prints, which already accounts for it.
What this breaks
- Self-connections. Two separate tickets booked on a mental estimate of arrival, rather than the printed time.
- Airport transfers. Booked for the wrong side of midnight.
- Car hire. Priced by 24-hour period from pick-up in local time.
- Arrival-day meetings. Especially eastbound, where the calendar date advances.
One extra trap
Overnight flights that cross a daylight saving transition. Twice a year a flight can appear an hour shorter or longer than the same service the previous week. The duration printed by the airline is correct; the arithmetic is what fails.
Transatlantic examples worked out
| Route | Ticket says | Looks like | Actual |
|---|---|---|---|
| London → New York | 10:00 → 13:00 | 3 hours | 8 hours |
| New York → London | 21:00 → 09:00 | 12 hours | 7 hours |
| London → Los Angeles | 11:00 → 14:30 | 3.5 hours | 11.5 hours |
| Frankfurt → Chicago | 13:00 → 15:30 | 2.5 hours | 9.5 hours |
Westbound the clock barely moves while you spend a working day in the air; eastbound the clock races ahead and swallows the night.
The formula
Duration = arrival local − departure local + (origin offset − destination offset). Easier still: read the duration the airline prints, which already accounts for both the zone difference and any daylight saving transition en route.
What gets booked wrong
- Self-connections. Two separate tickets, second one booked against a guessed arrival.
- Airport transfers. Ordered for the wrong side of midnight on eastbound red-eyes.
- Arrival-day meetings. A 09:00 arrival at Heathrow after an overnight is not a working morning.
- Parking and lounge bookings. Priced by local calendar day at each end.
The transition-week oddity
Twice a year an overnight transatlantic flight crosses a clock change, and the same service appears an hour shorter or longer than it did the week before. The printed duration is right; the arithmetic is what misleads.
Filed under Travel · Tags: flights, travel planning, connections. Figures verified against the official definitions — see our editorial policy.