Example 1
The destination month has fewer days. This tool clamps to its last valid day; it does not spill extra days into March.
Inputs
- Date
- 2026-01-31
- Operation
- Add
- Amount
- 1
- Unit
- Months
Calculated result
- Date
- 2026-02-28
Free time and date tool
Date Calculator
Move forward or backward from a starting date using calendar-aware units.
✓ Your time and date calculations are not stored.
Your result will appear here.
Worked examples you can reproduce
These fixed inputs are calculated by the same engine as the tool above. Compare the result and the boundary rule, then load an example to change one variable. Business-day examples do not subtract holidays.
Example 2
A leap-day anniversary is clamped to February 28 in a non-leap destination year. Check the policy if another convention is required.
Inputs
- Date
- 2024-02-29
- Operation
- Add
- Amount
- 1
- Unit
- Years
Calculated result
- Date
- 2025-02-28
Example 3
Two calendar weeks mean fourteen date steps. This is not a working-day or public-holiday calculation.
Inputs
- Date
- 2026-10-01
- Operation
- Subtract
- Amount
- 2
- Unit
- Weeks
Calculated result
- Date
- 2026-09-17
Detailed reading
Continue with the English editorial guides for worked reasoning, checklists, and source references.
Primary references
How it works
Add or subtract days, weeks, months or years from any calendar date.
- Choose the starting date.
- Select Add or Subtract and enter an amount.
- Choose days, weeks, months or years, then calculate the resulting date.
Example
Adding one month to January 31 uses calendar-aware month arithmetic rather than treating every month as 30 days.
How accuracy is handled
Month and year calculations follow real calendar lengths, including leap years.
Privacy: Inputs are validated and calculations use calendar-aware IANA time-zone rules.
Frequently asked questions
How are months handled?
PHP calendar arithmetic applies real month lengths.
Can I subtract time?
Choose Subtract and the desired unit.