Add one month to January 31 — date example.

A calendar month is not a fixed number of days. This example adds one month to January 31 in a leap year. Because February has no day 31, the calculator uses the last valid day of the target month: February 29.

2024-01-31 + 1 month

2024-02-29

Try it step by step

1. Keep the starting date at 2024-01-31, the amount at 1 and the unit at months.
2. Run the calculator and check that the result is 2024-02-29.
3. Repeat with 2025-01-31 to get 2025-02-28, then compare with adding 30 days.

How to read the result

The calculation moves to the target month and clamps the day to its last valid date. Adding 30 days to 2024-01-31 gives 2024-03-01 instead. Repeated one-month steps can differ from adding several months at once after an earlier step has reached a shorter month.

Limits and important details

The calculator works with calendar dates, not working days, holidays or contractual deadline rules. It does not decide which counting convention applies to a particular agreement.

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