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Month Calculator

Calculate the number of months between two dates, or add and subtract months from any date. The Month Calculator handles varying month lengths and end-of-month clamping automatically.

Formula

Months Between = (End Year − Start Year) × 12 + (End Month − Start Month) ± day adjustment

Example:

January 15 to August 3 → (0 years × 12) + 7 months − 1 (day adj.) = 6 months, 19 days

How to Calculate Months Between Two Dates

To find the number of complete months between two dates, subtract the years and months, then adjust for any remaining days.

Formula: Months = (Year₂ − Year₁) × 12 + (Month₂ − Month₁), adjusted if the day of the end date is earlier than the start date.

• Example: January 15 to August 3 = 6 months and 19 days (not 7 months, because Aug 3 comes before Jan 15's day-of-month)

When adding or subtracting months, the day is clamped to the last day of the target month if needed.

• Example: January 31 + 1 month = February 28 (or 29 in a leap year), not March 2 or 3.


See also