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Add or Subtract Time from a Date
Calculate a new date by adding or subtracting a duration, with correct handling of month ends and leap years.
- 100% local
- Instant
- Free
- No account
- Works offline
Enter a valid date and duration.
Resulting date
Why use this tool?
Add or subtract days, weeks, months or years from a date while correctly handling month ends and leap years in the shared date engine.
Smart processing
Generate, convert, or validate technical data with purpose-built controls.
Supported formats
Technical formats and syntaxes suited to each generator, converter, or validator.
Save time
Get a clean, ready-to-use result in seconds without installing software or configuring a complex workflow.
Fonctionnement
How does this tool work?
The engine starts from the selected date and applies the requested operation in the chosen unit. Days and weeks move directly through the calendar. For months and years, the engine preserves the original day when it exists in the target period; otherwise it uses the last valid day of the resulting month. This rule naturally handles month-end dates and leap years, with all calendar logic centralized in the shared engine rather than duplicated in the tool interface.
Use cases
Planning
Use this calculation to prepare a deadline or schedule with a value that can be checked immediately.
Verification
Check a result produced elsewhere and identify an input or method mistake more easily before using it.
Everyday use
Get an immediate answer for a common timing need without building a spreadsheet or repeating manual arithmetic.
Guide
How to use this tool
- 1
Enter the values
Provide the dates, times or durations requested by the tool.
- 2
Adjust the options
Choose the units or parameters that match your situation.
- 3
Review the result
The result recalculates automatically whenever an input changes.
Tips and best practices
- Check the entered values before using the result in a document, schedule or decision.
- The calculation runs locally in your browser and your data is not sent to a server.
- Reset the tool whenever you want to start a new scenario with clean inputs.
Frequently asked questions
Is the calculation automatic?
Yes. The result updates as soon as the required values are valid, without sending your data to a server.
Does my data stay local?
Yes. The entered information is processed directly in your browser by the shared Dates & time engine.
Can I change values after a calculation?
Yes. Change any input at any time and the result is immediately recalculated using the new values.
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