Month Calculator
Add or subtract months from any date, automatically handling month-end edge cases. Also compute the number of months between two dates with high precision.
About this Calculator
Add or subtract months from any date, automatically handling month-end edge cases. Also compute the number of months between two dates with high precision.
Formula & Calculations
Formula
Result Date = Start Date ± N months (with month-end clamping); Months Between = approximate based on day differentialWhere:
- Start Date=The reference date for the calculation
- End Date=The second date for calculating months between
- N=Number of months to add or subtract
Assumptions
- Month arithmetic caps the day to the last valid day of the target month (e.g., Jan 31 + 1 month = Feb 28/29).
- Months-between calculation divides total days by the average month length (30.44 days).
- Leap years are automatically accounted for.
Calculation Examples
Example 1
January 31 + 1 month lands on February 29 in the leap year 2024, since February has 29 days.
Example 2
Adding 6 months to January 15 yields July 15 with no month-end clamping needed.
Example 3
152 days ÷ 30.44 average days per month ≈ 5 months.
Frequently Asked Questions
What happens when adding months to the 31st of a month?
The calculator uses month-end clamping. For example, Jan 31 + 1 month becomes Feb 28 (or Feb 29 in leap years). Mar 31 + 1 month becomes Apr 30.
How precise is the 'months between' calculation?
The result is an approximation based on total days divided by the average month length (~30.44 days). For exact month boundaries, check each individual month's length.
Does this calculator handle negative months (subtraction)?
Yes. Enter a negative value to subtract months from a date. For example, -3 months from June 15 goes back to March 15.