Calculator · Difference & conversion
Time Difference Calculator
The time difference between two cities is the gap between their UTC offsets — not the gap you see on their clocks, and not a number baked into a table years ago. This time difference calculator works it out live from the IANA database, so it stays right through daylight saving, half-hour offsets and every historical rule change.
Live clocks
New York
EST / EDT
07:47
EDT · UTC−4
London
GMT / BST
12:47
BST · UTC+1
Berlin
CET / CEST
13:47
CEST · UTC+2
Dubai
UTC+4
15:47
UTC+4
Delhi
IST (UTC+5:30)
17:17
IST · UTC+5:30
Singapore
UTC+8
19:47
UTC+8
Tokyo
JST
20:47
JST · UTC+9
Sydney
AEST / AEDT
22:47
AEDT · UTC+11
Clocks update every 15 seconds in your browser and always reflect the current IANA daylight saving rules.
New York → London · Sat, Oct 24
London is currently 5 hours ahead of New York. Highlighted rows fall inside typical business hours (09:00–17:00 local, weekdays) in both cities.
| New York (EDT) | London (BST) |
|---|---|
| 00:00 | 05:00 |
| 01:00 | 06:00 |
| 02:00 | 07:00 |
| 03:00 | 08:00 |
| 04:00 | 09:00 |
| 05:00 | 10:00 |
| 06:00 | 11:00 |
| 07:00 | 12:00 |
| 08:00 | 13:00 |
| 09:00 | 14:00 |
| 10:00 | 15:00 |
| 11:00 | 16:00 |
| 12:00 | 17:00 |
| 13:00 | 18:00 |
| 14:00 | 19:00 |
| 15:00 | 20:00 |
| 16:00 | 21:00 |
| 17:00 | 22:00 |
| 18:00 | 23:00 |
| 19:00 | 00:00+1 day |
| 20:00 | 01:00+1 day |
| 21:00 | 01:00+1 day |
| 22:00 | 02:00+1 day |
| 23:00 | 03:00+1 day |
Swipe the table sideways for the full day
How a time difference is actually calculated
Every city has a UTC offset at any given instant. The difference between two cities is simply the difference between those two offsets — plus or minus, with no arithmetic on the clock faces themselves.
New York is UTC−5 in winter, so its offset difference against London (UTC+0) is 5 hours. Add the hour and London is 5 hours ahead. That sounds simple, and it is — but the two traps are that offsets change twice a year, and that not every offset is a whole number of hours.
Why the difference changes twice a year
When only one of the two cities observes daylight saving, the gap between them moves by one hour for half the year. When both observe it and switch on the same date, the gap stays the same all year but the labels change underneath it.
There is a nastier edge case: for one or two weeks in March and October or November, one country has already switched and the other has not. In that window the gap is genuinely one hour different from both the winter and the summer value. Only a converter that evaluates the actual rule for each date will get those days right — and they are exactly the days a recurring meeting falls on.
Time zones that are not whole hours
Some of the most populous places on Earth run on a half hour or a quarter of an hour offset, which makes "the difference" a decimal rather than a round number. Delhi is UTC+5:30 and Kathmandu is UTC+5:45, so the difference between them is 15 minutes. The Chatham Islands sit at UTC+12:45 and Eucla at UTC+8:45 — both three-quarter hours.
When you add a full-hour city to one of these, the result is a time that looks wrong at a glance: 09:00 in London is 14:30 in Delhi, and 09:00 in Auckland is 16:45 in Eucla.
- London → Delhi: 5 hours 30 minutes ahead (BST) or 5:30 (GMT + 5:30)
- London → Kathmandu: 5 hours 45 minutes ahead
- London → Eucla: 8 hours 45 minutes ahead
- New York → Tokyo: 13 hours ahead in summer, 14 in winter
- Los Angeles → Auckland: 19 hours ahead in summer, 20 in winter
Working examples you can check against
Worked through a few common pairs, using the current daylight saving state of each city:
- 09:00 New York → 14:00 London (5 hours ahead)
- 09:00 New York → 23:00 Tokyo the next day (13 hours ahead in summer)
- 16:00 Los Angeles → 00:00 Berlin the next day (8 hours ahead in summer)
- 10:00 London → 14:30 Delhi (5½ hours ahead)
- 09:00 Sydney → 21:00 London the previous day (11 hours behind in southern summer)
Adding and subtracting across the date line
Large differences usually push the date as well as the clock. A 19-hour difference between Los Angeles and Auckland means a Monday 09:00 in Los Angeles is Tuesday 04:00 in Auckland, and a Monday 09:00 in Auckland is Sunday 14:00 in Los Angeles. Getting the date right, not just the time, is what stops "wait, that was yesterday" moments.
The date changes when you cross the International Date Line, which runs through the Pacific and detours around Kiribati, Samoa and New Zealand so that whole countries stay together. It is why the date in Auckland and Los Angeles can differ by a full day even when the clocks look close.
Frequently asked questions
How do I calculate the time difference between two cities?
Look up the UTC offset of each city on the date in question and subtract one from the other. For example, New York is UTC−5 and London is UTC+0 in winter, so London is 5 hours ahead. Because offsets change with daylight saving, always use the offset for the specific date rather than a fixed number.
How many hours is New York behind London?
Five hours. New York is UTC−5 and London is UTC+0 in winter, and both switch to daylight saving on the same dates, so the gap stays five hours in summer too — even though the labels change from EST/GMT to EDT/BST.
What is the time difference between New York and Tokyo?
Thirteen hours ahead of New York during the northern summer (EDT, UTC−4) and fourteen hours ahead during the northern winter (EST, UTC−5). Tokyo itself never changes its offset.
Does the time difference change with daylight saving?
It can. When only one of the two cities observes daylight saving, the gap between them shifts by an hour for part of the year. When both switch at the same moment, the gap stays constant even though the labels change.
Why is the time difference to India not a whole number of hours?
India is UTC+5:30 and Nepal is UTC+5:45, so differences involving them are in half hours and quarter hours. A converter that only handles whole-hour offsets will be wrong by up to 45 minutes.