Quick answer
The difference is the second zone's offset minus the first's at noon on the date. On 15 January 2025, London (UTC+0) is 5 hours ahead of New York (UTC−5).
Enter a date and two zones. The calculator returns the difference and both offsets. Use this time zone difference calculator to check your own figures.
Related tools: Time Zone Converter: Convert a date and time from one time zone to another, including daylight saving. Time Zone Meeting Planner: The same meeting time in several time zones. Time Duration Calculator: Elapsed time between two clock times, including across midnight.
How to use the Time Zone Difference Calculator
- Pick date.
- Choose first zone: UTC, America/New York, America/Chicago, America/Denver, America/Los Angeles and America/Anchorage and 32 more.
- Choose second zone: UTC, America/New York, America/Chicago, America/Denver, America/Los Angeles and America/Anchorage and 32 more.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Date | A calendar date | — |
| First zone | Choose one: UTC; America/New York; America/Chicago; America/Denver; America/Los Angeles; America/Anchorage; Pacific/Honolulu; America/Toronto; … | Starts at America/New York |
| Second zone | Choose one: UTC; America/New York; America/Chicago; America/Denver; America/Los Angeles; America/Anchorage; Pacific/Honolulu; America/Toronto; … | Starts at Europe/London |
Formula and method
Formula
difference = offset of the second zone − offset of the first, at noon on the date
IEEE-754 double precision; shown to at most 6 decimal places.
Differences change when either place starts or ends daylight saving, so the date matters.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Date = 2025-01-15; First zone = America/New York; Second zone = Europe/London.
| Result | Value |
|---|---|
| Time difference | +5 hours |
| Offset of the first zone | UTC-5 |
| Offset of the second zone | UTC+0 |
Example 2
Inputs: Date = 2025-03-20; First zone = Asia/Kolkata; Second zone = America/Los Angeles.
| Result | Value |
|---|---|
| Time difference | -12.5 hours |
| Offset of the first zone | UTC+5:30 |
| Offset of the second zone | UTC-7 |
Example 3
Inputs: Date = 2025-04-10; First zone = Australia/Sydney; Second zone = Pacific/Auckland.
| Result | Value |
|---|---|
| Time difference | +2 hours |
| Offset of the first zone | UTC+10 |
| Offset of the second zone | UTC+12 |
The first line is the headline result (time difference). Below it the time Zone Difference Calculator lists offset of the first zone and offset of the second zone, which describe the same case from other angles. IEEE-754 double precision; shown to at most 6 decimal places.
Why a date
The gap changes with daylight saving. Between US and UK changeovers, New York can be only 4 hours behind London.
Transitions
The difference can change within a single day around a transition, so the tool measures at noon.
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Date: left empty shows "Enter date." beside that field and no result.
Choosing between the Time Zone Difference Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Time Zone Converter](/time/time-zone-converter/) | date, time and from | Converted time |
| [Time Zone Meeting Planner](/time/time-zone-meeting-planner-calculator/) | date, time and your time zone | Your time |
| [Time Duration Calculator](/time/time-duration-calculator/) | start time and end time | Duration |
| [Time Card Calculator](/time/time-card-calculator/) | start times, end times and unpaid break per day | Total time |
| [Time From Now Calculator](/time/minutes-from/) | start time and minutes to add | Resulting time |
Background: dates and times
Date and time results depend on the conventions a tool uses: whether the end date counts, whether weekends and holidays are skipped, how months of different lengths are handled and whether time zones are applied. This page states its convention, and the worked examples show it.
Dates use the Gregorian calendar and calendar days unless the page says otherwise; check deadlines against the rule in your contract or regulation.
Assumptions and limitations
- The difference can change within a single day around a transition
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for date to confirm this.
Frequently asked questions
India versus UTC?
India Standard Time is UTC+5:30 all year, since India doesn't observe daylight saving.
Do all zones use whole hours?
No, some use 30 or 45 minutes.
What if both observe DST?
The gap is often unchanged.
What does the Time Zone Difference Calculator calculate?
Hours between two time zones on a given date. It returns Time difference, Offset of the first zone and Offset of the second zone.
What formula does the Time Zone Difference Calculator use?
difference = offset of the second zone − offset of the first, at noon on the date. Differences change when either place starts or ends daylight saving, so the date matters.
What do I need to enter in the time Zone Difference Calculator?
You enter Date, First zone and Second zone.
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. The difference can change within a single day around a transition.
What is an example of a time Zone Difference result?
With date 2025-01-15, first zone America/New York and second zone Europe/London, the time difference is +5 hours.
Where does the method come from?
The method follows: IANA Time Zone Database (tz database) as implemented in the runtime's ICU data; daylight saving rules apply on the date entered.
Related calculators
- Time Zone Converter — Convert a date and time from one time zone to another, including daylight saving.
- Time Zone Meeting Planner — The same meeting time in several time zones.
- Time Duration Calculator — Elapsed time between two clock times, including across midnight.
- Time Card Calculator — Total hours, overtime and gross pay from daily start and end times.
- Time From Now Calculator — Clock time after adding or subtracting minutes.
- Time Until Calculator — Hours and minutes from the current time until a target clock time (generalizes “how long until 3:58 PM”).
Sources
- IANA Time Zone Database (tz database) as implemented in the runtime's ICU data; daylight saving rules apply on the date entered
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.