Add Months Calculator
Add or subtract calendar months and handle shorter destination months explicitly.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Calendar date | Gregorian calendar date in YYYY-MM-DD format; years 0001 through 9999. |
| Months | integer -120000..120000 |
Understanding your result
Calendar results use the stated counting and anniversary convention. Complete months and years differ from fixed day counts.
Common mistakes
- Counting both end dates when the method excludes a boundary, or assuming all months have equal length.
Check your calculation
- Test a short known interval and a leap-day boundary; for working days, verify your holiday list.
Calculation checks, sources and review limits
What date is a given number of calendar months after or before this date?
Add or subtract calendar months and handle shorter destination months explicitly.
Common uses
- Add or subtract calendar months and handle shorter destination months explicitly.
How it works
Shift year/month index by integer months; clamp day to destination month length. Calendar arithmetic uses the proleptic Gregorian calendar. Explicit calendar dates are independent of local daylight-saving changes. Month/year additions clamp to the last valid day of the destination month. Timestamp arithmetic requires a stated UTC offset and excludes leap seconds.
Worked example
Enter Calendar date: 2024-01-31; Months: 1. The result is Date: 2024-02-29.
FAQ
What date is a given number of calendar months after or before this date?
Shift year/month index by integer months; clamp day to destination month length. Calendar arithmetic uses the proleptic Gregorian calendar. Explicit calendar dates are independent of local daylight-saving changes. Month/year additions clamp to the last valid day of the destination month. Timestamp arithmetic requires a stated UTC offset and excludes leap seconds.
What assumptions and limits apply?
Clamping is explicit product convention. Reject resulting years outside 1..9999.