Months Between Dates Calculator
Enter the start and end dates.
Your numbers
Your results
Months and days
Months and days
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Decimal months (average month of 30.44 days)
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Weeks
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Days
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Months Between Dates Calculator by TheCalcTools
How the Months Between Dates Calculator works
Whole months are counted on the calendar from the start date; if the end day is earlier in the month than the start day, the last month is not complete. When the start is the 31st and a month is shorter, the anniversary falls on that month’s last day.
Decimal months divide the days by the average Gregorian month length, 30.436875 days.
The formula
Decimal months = days ÷ 30.436875
Worked example
Using the default values shown in the calculator:
| Start date | 2025-01-31 |
|---|---|
| End date | 2026-10-17 |
- From 31 January 2025 to 17 October 2026: 20 months and 17 days (624 days).
Result:
| Months and days | 20 months and 17 days |
|---|---|
| Decimal months (average month of 30.44 days) | 20.50 |
| Weeks | 89.1 |
| Days | 624 |
Frequently asked questions
How many months from 31 January to 28 February?
One month: the anniversary falls on the last day of February.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.