Date and time difference
Date and time difference lets you calculate elapsed milliseconds, seconds, and duration between instants in your browser.
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.
Add or subtract date/time
⌂ Inputs and results stay in this browser and are not automatically stored or sent.
Waiting for input
Input
Years, months and days use calendar arithmetic; hours use elapsed time. Use negative amounts to subtract.
Output
Waiting for input
Complete text result
How to use
Enter the starting date/time, time zone, and calendar or clock units to add or subtract.
Check the month-end constrain policy when the destination date does not exist. One month is not always 30 days; inspect the resulting date and UTC offset together.
Examples
2026-01-31T12:00:00ZPrinciples 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
Business day calculator
Business day calculator lets you count inclusive business days excluding chosen weekdays and entered holidays in your browser.