Months Between Dates
Calculate the exact number of months and days between two dates.
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How to use this calculator
- 1
Select the start date.
- 2
Select the end date.
- 3
The result shows complete months plus remaining days, and the approximate decimal months.
Frequently asked questions
How does this tool count complete months?
It counts whole calendar months forward from the start date and then reports the leftover days. January 15 to April 3, 2026 is 2 months and 19 days, because January 15 plus 2 months is March 15, and April 3 is 19 days after that. The months figure includes whole years, so a span of three years and two months shows as 38 months.
What happens when the start date is the 29th, 30th or 31st?
When the target month is too short, the date is clamped to that month’s last day, as implemented in the shared date utilities. August 31, 2025 plus 6 months is February 28, 2026, so those two dates are exactly 6 months and 0 days apart. January 31 to March 1, 2026 is 1 month and 1 day.
How is February 29 treated?
In a common year its anniversary falls on February 28. From February 29, 2024 to February 28, 2025 the tool shows 12 months 0 days over 365 days, and February 29, 2024 to February 29, 2028 shows exactly 48 months.
Why is Decimal Months not the same as the month count?
Decimal Months is total days ÷ 30.44, an average-length month, while the headline figure counts calendar months. January 31 to March 1, 2026 is 29 days, so it shows 0.95 decimal months next to 1 month 1 day. They answer different questions, so use whichever your agreement specifies.
What does it show when the end date is before the start date?
The months-and-days result is wrapped in a minus sign, such as −(1 months 1 days) for March 1 back to January 31, 2026, and the decimal months and total days carry a minus sign as well. The size of the gap is the same as in the forward direction.
Are the start and end days both counted?
No. It measures the distance between the dates, so the same date twice gives 0 months 0 days. If your contract counts both days, add one day to the leftover days.
What does it do with blank or invalid dates?
It shows a dash instead of a result, rather than guessing a date.
Does it ignore weekends, holidays or time of day?
It uses calendar dates only, with no time of day, no weekends excluded and no holiday data. For weekdays only, use the working days calculator.
Months between dates — calendar months plus leftover days
Calendar months are not a fixed length
A month can be 28, 29, 30 or 31 days, so a count of months depends on where you start. The calculator steps forward one calendar month at a time from the start date, using the same date in the next month, and stops at the last whole month that does not overshoot the end date. Whatever remains is reported as days. Because the stepping begins from the start date, the same number of days can produce a different month count depending on which months are involved, and that is the correct behaviour for leases, subscriptions and loan terms that renew on a calendar date.
Worked examples
Seven fixed pairs of dates were run through the calculator. The table lists the months-and-days breakdown, the decimal month figure and the day total for each, including month-end starts, a leap-day span and a reversed pair.
| Start | End | Months + days | Decimal months | Total days |
|---|---|---|---|---|
| 2026-01-15 | 2026-04-03 | 2 months 19 days | 2.56 | 78 |
| 2025-12-15 | 2026-03-15 | 3 months 0 days | 2.96 | 90 |
| 2026-01-31 | 2026-03-01 | 1 months 1 days | 0.95 | 29 |
| 2025-08-31 | 2026-02-28 | 6 months 0 days | 5.95 | 181 |
| 2024-02-29 | 2025-02-28 | 12 months 0 days | 11.99 | 365 |
| 2020-01-01 | 2023-03-15 | 38 months 14 days | 38.40 | 1,169 |
| 2026-03-01 | 2026-01-31 | −(1 months 1 days) | −0.95 | −29 |
Month-end starts
The awkward cases begin on the 29th, 30th or 31st. Counting forward from January 31 by one month cannot land on February 31, so the date is pulled back to the end of February. That is why August 31 to February 28 comes out at exactly six months with no remainder, and why January 31 to March 1 reads as 1 month and 1 day. The behaviour matches the date-difference calculator on this site because both rely on the same date utilities, so the two pages will agree for the same pair of dates.
Calendar months versus decimal months
Two figures are offered because finance and legal documents ask different questions. The headline is a calendar count: whole months plus days. The decimal figure divides total days by 30.44, the average month length, which is useful for pro-rata sums but never lines up exactly with the calendar. The 2025-12-15 to 2026-03-15 row illustrates the gap: it is exactly 3 calendar months, yet 90 days gives 2.96 decimal months. Quote whichever your document defines.
What it does not do
Only dates are compared. It has no time-of-day, time-zone, weekend or holiday logic, and it does not count the end date as an extra day. Reversed dates return the same-sized gap wrapped in a minus sign. If you need an exact day count for interest or notice periods, use the Total Days line, and if you need an exact date a number of months ahead, use the date calculator instead.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →