Time Zone Difference Calculator
Scheduling a call across the world, or just working out what time it is for someone else, comes down to one number: how many hours apart two places are. This calculator finds that gap from the cleanest possible inputs, the two zones' offsets from Coordinated Universal Time, the global clock reference that every time zone is measured against. You enter the UTC offset for each location, and it returns the difference in hours and tells you which place is ahead. The method is a single subtraction: take the second location's offset minus the first location's offset, and a positive result means the second place is ahead while a negative one means it is behind. Because offsets are simply hours relative to UTC, this avoids the confusion of comparing clock times directly. The offset field accepts decimals, so half-hour and quarter-hour zones such as UTC plus 5:30 or plus 5:45 are entered as 5.5 or 5.75 and still calculate correctly. Remember that daylight saving time shifts a region's offset by an hour, so use the offsets in effect on the date you care about. Every figure here is computed deterministically from your two offsets, and the worked example below reconciles exactly to the calculator.
The time gap is the second offset minus the first: difference = offset 2 - offset 1. New York at UTC-5 and London at UTC+0 differ by 5 hours, with London ahead.
Time zone difference formula
difference = o2 - o1
o1 = UTC offset of the first location
o2 = UTC offset of the second location
positive = second location is ahead
Both offsets are measured against the same reference, UTC, so subtracting one from the other gives the hours between the two local clocks directly, with the sign telling you which place is ahead.
Worked example
Compare New York, at UTC minus 5, with London, at UTC plus 0.
- First offset: o1 = -5
- Second offset: o2 = 0
- Difference: 0 - (-5) = 5 hours
London is 5 hours ahead of New York. These are the calculator's default inputs, so the result above matches the widget exactly.
Selected UTC offsets (standard time)
Offsets change by an hour where daylight saving is observed.
| City | UTC offset |
|---|---|
| Los Angeles | -8 |
| New York | -5 |
| London | 0 |
| Mumbai | +5.5 |
| Tokyo | +9 |
| Sydney | +10 |
Civil time and time zone standards: US National Institute of Standards and Technology (NIST).
Time zone difference calculator: frequently asked questions
How do I calculate the time difference between two time zones?
Subtract the first place's UTC offset from the second place's UTC offset. The result is how many hours the second place is ahead, or behind if negative. New York at UTC minus 5 and London at UTC plus 0 differ by 0 minus negative 5, which is 5 hours, so London is ahead.
What is a UTC offset?
It is how far a time zone is from Coordinated Universal Time, the global reference. UTC plus 1 is one hour ahead of UTC, UTC minus 8 is eight hours behind. Most clocks around the world are described by their offset from UTC, which makes comparing two zones a simple subtraction.
Does daylight saving time change the result?
Yes. When a region shifts to daylight saving, its UTC offset changes by an hour, so the gap between two zones can vary across the year if one observes daylight saving and the other does not. Enter the offsets that are actually in effect on the date you care about.
Why might the difference be more than 12 hours?
Offsets range from about UTC minus 12 to UTC plus 14, so two extreme zones can be more than a full half-day apart, up to 26 hours in rare cases. A difference over 12 hours simply means the two places are far around the globe from each other.
Can offsets include half or quarter hours?
Yes. Some zones use offsets such as UTC plus 5:30 or UTC plus 5:45. Enter the offset as a decimal, for example 5.5 for five and a half hours or 5.75 for five and three quarter hours, and the subtraction still works correctly.
Official sources
- Civil time, time zones and the UTC reference: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.