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Time & Date

Months Between Dates Calculator

From January 15, 2025 to July 15, 2026 is 18 months, or 1 year and 6 months. This calculator finds the number of calendar months between two dates using calendar-aware math. Unlike a simple day count divided by 30, this calculator respects actual month boundaries and handles leap years and short months correctly.

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Quick answer

Calendar months are counted by how many month transitions fit between the two dates.

Months between

18 months

Years and months

1 year, 6 months

Total weeks

78

What this tells you

  • •Calendar months are counted by how many month transitions fit between the two dates.
  • •If the start date's day number exceeds the end date's day number, the partial month does not count.
  • •Leap years and month lengths are handled by the JavaScript Date engine.
  • •Total weeks are also shown as a cross-check against month counts.
  • •Results include a years-and-months breakdown for readability.

How to Use

  1. 1Enter a start date and an end date. The end date must be after the start date.
  2. 2The calculator counts full calendar months between the two dates.
  3. 3The years-and-months breakdown splits the total into whole years and remaining months.
  4. 4Total weeks are calculated from the day count for verification.

How It Works

Formula

months = (end year - start year) × 12 + (end month - start month), adjusted if partial month

Count the number of month transitions between the two dates. If the start day of the month is later in the month than the end day, subtract one month because that last month is not complete. For January 15 to April 10, April has not reached the 15th yet, so only January through March count as full months.

Calculation note: values are processed in the order shown above, using the current input units.

Worked Examples

18 months span

Start Date2025-01-15
End Date2026-07-15
Result18 months (1 year, 6 months)

Short span under a year

Start Date2026-01-15
End Date2026-04-10
Result2 months

Months Between Common Date Ranges

StartEndMonthsYears & Months
Jan 1, 2025Dec 31, 20251111 months
Jan 15, 2025Jan 15, 2026121 year
Mar 1, 2024Mar 1, 2026242 years
Jun 1, 2025Dec 1, 2026181 year, 6 months

Common mistakes

  • Using 30 days per month as a shortcut. Calendar months range from 28 to 31 days, and accumulated rounding error can misstate the count.
  • Counting the partial month at the end as a full month. The calculator counts only complete calendar months.
  • Forgetting to adjust for the day of the month. A span from January 31 to February 28 may not count as a full month.

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Embed this calculator on your site

Drop this single line where you want the calculator to appear. It is responsive, mobile-friendly, resizes automatically, and is free to use with attribution.

<script src="https://calctide.com/embed.js" data-tool="months-between-calculator" async></script>

Preview the embed at /embed/months-between-calculator/.

Frequently Asked Questions

Count the number of full calendar months that fit between the two dates. From January 15 to July 15 is 6 months if the year is the same. If the years differ, add 12 months for each full year between them.
A month is a calendar month, from the first day to the last. The calculator counts month transitions, not 30-day blocks. February counts as one month even though it has fewer days than January.
If the end date's day number is earlier in the month than the start date's day number, the final month is not complete and is not counted. January 31 to February 28 does not cross the 31st in February, so it does not count as a full month.
A date difference calculator shows the gap in days, weeks, months, and years simultaneously. This calculator focuses specifically on calendar months, with a cleaner output for people who only need the month count.
It estimates months between dates calculator outputs using the visible inputs and formula assumptions on this page.

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