Quick answer
The converter turns a local time into a UTC instant and then into the target zone. 09:00 in New York on 15 January 2025 is 14:00 in London (UTC−5 to UTC+0), a difference of +5 hours.
Enter a date, time and two zones. The calculator returns the converted time, weekday and offsets.
Related tools: Time Zone Difference Calculator: Hours between two time zones on a given date. 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 Converter
- Pick date.
- Type time (24-hour), for example 09:00.
- Choose from: UTC, America/New York, America/Chicago, America/Denver, America/Los Angeles and America/Anchorage and 32 more.
- Choose to: 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 | — |
| Time (24-hour) | Text, such as 09:00 | — |
| From | Choose one: UTC; America/New York; America/Chicago; America/Denver; America/Los Angeles; America/Anchorage; Pacific/Honolulu; America/Toronto; … | Starts at America/New York |
| To | 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
local time → UTC instant → local time in the target zone
IEEE-754 double precision; shown to at most 6 decimal places.
Uses the IANA time zone database, so daylight saving changes are applied for the date you enter. A local time that does not exist (spring-forward gap) is moved forward.
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; Time (24-hour) = 09:00; From = America/New York; To = Europe/London.
| Result | Value |
|---|---|
| Converted time | 2025-01-15 14:00 |
| Weekday | Wednesday |
| Offset of the source zone | UTC-5 |
| Offset of the target zone | UTC+0 |
| Difference | +5 hours |
Example 2
Inputs: Date = 2025-03-09; Time (24-hour) = 12:00; From = America/Los Angeles; To = Asia/Kolkata.
| Result | Value |
|---|---|
| Converted time | 2025-03-10 00:30 |
| Weekday | Monday |
| Offset of the source zone | UTC-7 |
| Offset of the target zone | UTC+5:30 |
| Difference | +12.5 hours |
Example 3
Inputs: Date = 2025-07-01; Time (24-hour) = 23:30; From = Australia/Sydney; To = America/Chicago.
| Result | Value |
|---|---|
| Converted time | 2025-07-01 08:30 |
| Weekday | Tuesday |
| Offset of the source zone | UTC+10 |
| Offset of the target zone | UTC-5 |
| Difference | -15 hours |
The first line is the headline result (converted time). Below it the time Zone Converter lists weekday, offset of the source zone, offset of the target zone and difference, which describe the same case from other angles. IEEE-754 double precision; shown to at most 6 decimal places.
Daylight saving
Offsets depend on the date. In summer New York is UTC−4 and London UTC+1, still 5 hours apart, but for a few weeks in March and late October the gap changes.
Ambiguous times
Ambiguous times at the end of daylight saving use the first occurrence. Zones are named by region, such as America/New_York.
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.
- Time (24-hour): entering "25:00" shows "Enter a time like 09:30 (24-hour)." beside that field and no result.
Choosing between the Time Zone Converter 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 Difference Calculator](/time/time-zone-difference-calculator/) | date, first zone and second zone | Time difference |
| [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
- Ambiguous times at the end of daylight saving use the first occurrence
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 and time (24-hour) to confirm this.
Frequently asked questions
What is 9am New York in Tokyo?
11pm the same day in winter.
Is UTC the same as GMT?
Practically, for ordinary use.
Why a date?
Offsets change with daylight saving.
What does the Time Zone Converter calculate?
Convert a date and time from one time zone to another, including daylight saving. It returns Converted time, Weekday, Offset of the source zone, Offset of the target zone and Difference.
What formula does the Time Zone Converter use?
local time → UTC instant → local time in the target zone. Uses the IANA time zone database, so daylight saving changes are applied for the date you enter.
What do I need to enter in the time Zone Converter?
You enter Date, Time (24-hour), From and To.
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. Ambiguous times at the end of daylight saving use the first occurrence.
What is an example of a time Zone result?
With date 2025-01-15, time (24-hour) 09:00, from America/New York and to Europe/London, the converted time is 2025-01-15 14:00.
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 Difference Calculator — Hours between two time zones on a given date.
- 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.