Time Zone & Jet Lag Calculator
Convert times between cities, find the hours when your remote team is all at work, and estimate how long your body clock needs to catch up after a flight
Plan Across Time Zones
Planning estimate only. Not medical advice; ask a doctor about sleep disorders or the timing of any medication.
How to use this tool
- In Converter, pick the two cities, a date and a time to see the time in the other city.
- In Team Overlap, add each person's city and working hours to find the hours when everyone is at work.
- In Jet Lag, pick origin, destination, departure date and travel time.
- Read the result and use Copy Result to share it.
Worked example
On October 8, 2026, 09:00 in New York is 14:00 in London, a 5-hour difference, because both cities are on daylight saving time. Change the date to October 26, 2026 and the same 09:00 becomes 13:00, a 4-hour difference: the UK has returned to standard time (UTC+0) while New York is still on UTC−4. That is why the tool reads the offset for the exact date you choose. For a New York to London flight the clock shift is +5 hours eastbound, which the tool estimates at about 5 days to adapt (1.0 day per hour east, 0.65 per hour west). These are planning estimates, not medical advice.
Methodology
Every conversion reads the IANA Time Zone Database built into your browser through the ECMAScript Intl.DateTimeFormat API, so daylight saving rules are applied for the exact date you choose, not for today's offset.
Hannah's flight on the weekend the clocks change
Hannah flies from Berlin to New York on Sunday, October 25, 2026, leaving at 10:00 with a 9-hour travel time. That is the very morning Europe switches back to standard time, while the US is still on daylight saving time for another week. Here is what the Jet Lag tab does with it.
- Departure offset (Berlin, read on the departure date): UTC+1. Arrival offset (New York, read on the arrival date): UTC−4.
- Clock shift: −4 − (+1) = −5 hours, westbound. Arrival is 14:00 New York time the same day.
- Adaptation: 5 × 0.65 = 3.25, rounded to the nearest half day: 3.5 days. Impact: Moderate.
- Day by day: about 3.5 h off after day 1, 1.9 h after day 2, 0.4 h after day 3, adapted on day 4.
One week earlier, on October 18, the same flight shows a −6 hour shift, 4 days and a Strong impact, because Berlin was still on UTC+2. Hannah would have guessed 6 hours from habit and planned a day too many. She keeps the Sunday departure and, per the tool's westbound tip, plans for bright light in the late afternoon. This is a planning estimate, not medical advice.
Long-Haul & Remote Travel Essentials
Gear that helps you rest on the plane and keep your devices powered in any country
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Ceptics 45W Universal Travel Adapter, 3 USB-A + 2 USB-C
Plug types A, C, G and I cover the US, continental Europe, the UK and Australia, and it charges up to five devices at once (45 W over USB-C).
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Frequently asked questions
Why does the time difference between New York and London change in March and October? ▼
Because the US and Europe switch daylight saving time on different dates. The US changes on the second Sunday of March and the first Sunday of November, while the UK and EU change on the last Sundays of March and October. For a few weeks in spring and about one week in autumn, New York and London are 4 hours apart instead of the usual 5.
What if nobody on the team has overlapping working hours? ▼
The tool then shows the best compromise window: the longest stretch in which the largest number of people are inside their hours. New York and Tokyo on 9:00–17:00 schedules, for example, share no hour at all, so the realistic options are stretching one side's hours or rotating the inconvenient slot.
Is jet lag really worse when flying east than west? ▼
For most travelers, yes. Going east asks your body clock to advance, which is harder than delaying it. The calculator uses 1 day per hour of shift eastbound and about 0.65 day westbound, so a 6-hour eastbound trip is estimated at 6 days but a 6-hour westbound trip at about 4 days.
Why does a jet lag calculator need the flight duration? ▼
It fixes the exact arrival moment. If clocks change at the destination between the day you leave and the day you land, the real shift differs by an hour, so this tool reads each city's UTC offset at its own date and time instead of assuming one fixed difference.
Why do some results show half-hour or 45-minute differences? ▼
Some regions do not use whole-hour offsets: India is UTC+5:30, Nepal is UTC+5:45 and Adelaide is UTC+9:30 in winter and UTC+10:30 in summer. The tool handles quarter- and half-hour differences exactly, which a mental subtract-the-hours shortcut gets wrong.