Add or subtract date/time
Add or subtract date/time lets you add calendar and clock units with explicit time zone and month-end constrain policy in your browser.
Date and time difference
Date and time difference lets you calculate elapsed milliseconds, seconds, and duration between instants in your browser.
Date and time difference
⌂ Inputs and results stay in this browser and are not automatically stored or sent.
Waiting for input
Input
Include Z or a UTC offset to avoid depending on your device time zone.
Output
Waiting for input
Complete text result
How to use
Enter start and end times, including offsets or time zones when relevant.
Elapsed seconds and calendar-date differences answer different questions. A day across a daylight-saving change is not necessarily 24 elapsed hours; choose the interpretation your task requires.
Examples
2026-01-01T00:00:00Z
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2026-01-02T12:30:00ZPrinciples and limits
Each input is limited to 1,048,576 bytes, output to 33,554,432 bytes, and processing to 5,000 ms. Input is never silently truncated.
Guides
Related tools
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Duration converter lets you convert seconds and ISO 8601 durations without treating months or years as fixed seconds in your browser.
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Business day calculator lets you count inclusive business days excluding chosen weekdays and entered holidays in your browser.