Time Difference Calculator

Compare two time zones (Time Zones tab)

Use the Time Zones tab to find the hour gap between any two cities or time zones on a specific calendar date. The calculator applies IANA time zone rules for the selected date and time.

1. Select Zone A and Zone B from the dropdown lists. The dropdowns are grouped by region for quick scanning.
2. Choose a date. Daylight Saving Time rules are applied based on the date you select, not today's date, so you can calculate the difference on any past or future date.
3. Enter a time in Zone A — for example, 9:00 AM — and click Calculate. The result shows the matching time in Zone B, the offset for each zone, and whether Zone B falls on the same day, the next day, or the previous day.

Example: New York and London on 2026-05-15 at 9:00 AM. New York is on EDT (UTC-4), London is on BST (UTC+1) — a 5-hour difference. The result shows London at 2:00 PM on the same day.

Calculate elapsed time between two clock readings (Two Times tab)

Use the Two Times tab to find how much time elapsed between any start and end time on the same day. No date or time zone is needed — this mode works with pure clock times.

1. Enter a start time using the time input (HH:MM format).
2. Enter an end time.
3. If the period crosses midnight — for example, 10:00 PM start to 6:00 AM end — enable Spans midnight. Without this toggle, an end time earlier than the start time is treated as invalid.
4. Click Calculate. The result shows the elapsed time in hours and minutes, decimal hours, total minutes, and total seconds.

Example: 9:30 AM to 5:45 PM is 8 hours 15 minutes (8.25 decimal hours, 495 total minutes, 29,700 seconds). With Spans midnight enabled, 10:00 PM to 6:00 AM is 8 hours.

How Daylight Saving Time affects results

Many countries advance their clocks by 1 hour in spring and revert in autumn — Daylight Saving Time (DST). When two cities both observe DST but change on different dates, there is a brief period each year where the offset between them differs from its usual value.

For example, the US changes on the second Sunday of March; most of Europe changes on the last Sunday of March. In the weeks between these dates, New York is already on EDT (UTC-4) while London is still on GMT (UTC+0), giving a 4-hour difference instead of the usual 5. Select 2026-03-08 in the calculator to see this in action.

This calculator reads IANA timezone rules to determine the correct offset for any date — including transition days. The result card always shows the offset with its abbreviation (EDT, BST, GMT, etc.) so you can see exactly which rule applied.

Time Difference Calculator vs. related tools

Time Duration Calculator — calculates how long a period lasted, with optional break subtraction and support for full date-range inputs spanning days, weeks, or months. Use it when you need to measure a work session, shift, or any timed interval. The Time Difference Calculator is optimized for comparing zone offsets or two clock times without break deductions.

Time Zone Calculator — converts a specific time from one time zone to another. Use it when your main question is “what time is it there?” rather than “how many hours apart are these places?” Use the Time Zones tab on this calculator when you need to compare offsets or convert a time on a specific date with DST taken into account.

Military Time Converter — converts between 12-hour AM/PM, 24-hour, and military time formats. Use it when the input or output needs to be in military notation rather than a time zone comparison.

Decimal Hour Calculator — converts between hours-and-minutes format and decimal hours. Use it when you need the result in decimal format for payroll, billing, or spreadsheet input.