How many months between dates?
Enter two dates to see how many months are between them. The end date starts as today, so the page also counts the months since a date.
- Months
- 6 months
From March 30, 2026 to September 30, 2026 is 6 months (6 in decimal months).
- In months
- 6
- In years, months, and days
- 6 months
- Days
- 184
Answer for the example date Wednesday, September 30, 2026. It changes to today's date when the page loads.
Months: 6 months. From March 30, 2026 to September 30, 2026 is 6 months (6 in decimal months).
Where are the dates on the calendar?
How to calculate
Counts the months between two dates: whole months and days, the same span as a decimal number of months, in years, months, and days, and in days.
Example with the default inputs (Start date March 30, 2026, End date September 30, 2026) on the example date Wednesday, September 30, 2026: From March 30, 2026 to September 30, 2026 is 6 months (6 in decimal months).
Method: months = the most whole months M with start + M months ≤ end; decimal months = M + (end − (start + M months)) ÷ ((start + (M + 1) months) − (start + M months))
- Dates are whole calendar days in the Gregorian calendar, with no time of day.
- Adding months keeps the day of the month; a day that the month does not have moves to its last day, so January 31 plus 1 month is February 28 (or 29).
- The end date is today unless you change it; the page reads today’s date from your device when it loads.
- A start date after the end date has no answer.
Worked examples
Each example is checked against the calculator on every build.
- Start date 2026-01-15, End date 2026-09-30 gives Months 8 months, 15 days, In months 8.5, In years, months, and days 8 months, 15 days, Days 258.Source: Julian Day numbers (Meeus, Astronomical Algorithms, 1991, chapter 7): JD 2461313.5 − JD 2461055.5 = 258 days
- Start date 2026-01-31, End date 2026-03-15 gives Months 1 month, 15 days, In months 1.483871, Days 43.Source: Gregorian calendar month lengths (ISO 8601)
- Start date 2025-11-30, End date 2026-02-28 gives Months 3 months, In months 3, Days 90.Source: Gregorian calendar month lengths (ISO 8601)
- Start date 2024-03-10, End date 2026-05-20 gives Months 26 months, 10 days, In months 26.322581, In years, months, and days 2 years, 2 months, 10 days.
How it works
Dates are whole calendar days in the Gregorian calendar, with no time of day. Dates from January 1, 1600 to December 31, 2400 are accepted, and the start date must be on or before the end date; otherwise there is no answer.
Adding M months to a date keeps its day of the month in the month M months later. If that month is shorter than the day (the 31st in a 30-day month, or the 29th to 31st in February), the date moves to the month’s last day. Each monthly date is counted from the start date, not from the one before: January 31 plus 2 months is March 31, even though January 31 plus 1 month is February 28.
- Months: the most whole months M such that the start date plus M months is not after the end date, and the days left from that date to the end date.
- In months = M + d ÷ L, where d is the days left and L is the days from the start date plus M months to the start date plus M + 1 months (28 to 31). It shows to 2 decimal places.
- In years, months, and days: the same whole months as years (M ÷ 12, rounded down) and months (the rest), with the same days left.
- Days = end date − start date, in whole days.
The end date starts as today and the start date as 6 months before today. The page was built on one day and may be opened on another: the built page shows the dates of its build day, and your browser replaces them with yours as soon as the page loads.
Worked examples by hand
January 15, 2026 to September 30, 2026. January 15 plus 8 months is September 15; plus 9 months would be October 15, after the end date. So 8 months and 15 days. The next monthly date, October 15, is 30 days after September 15: 8 + 15 ÷ 30 = 8.5 months. In days: 16 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 = 258 days.
January 31, 2026 to March 15, 2026. January 31 plus 1 month is February 28 (2026 is not a leap year). Plus 2 months is March 31, after the end date. So 1 month and 15 days (February 28 to March 15). The next monthly date is March 31, 31 days after February 28: 1 + 15 ÷ 31 = 1.48 months. In days: 43.
November 30, 2025 to February 28, 2026. November 30 plus 3 months is February 28, 2026 (February has no 30th), which is the end date: exactly 3 months, 90 days.
March 10, 2024 to May 20, 2026. March 10, 2024 plus 26 months is May 10, 2026, and 10 more days is May 20: 26 months and 10 days, or 2 years, 2 months, and 10 days. May 10 to June 10, 2026 is 31 days: 26 + 10 ÷ 31 = 26.32 months.
Other questions people ask
How do I count the months between two dates?
Step forward from the start date one month at a time, keeping the same day of the month, until one more step would pass the end date. Those are the whole months; the days from there to the end date are the days left. From January 15 to September 30, 2026 is 8 months and 15 days.
How does the calculator handle the 31st of a month?
A day that a month does not have moves to the last day of that month. So January 31 plus 1 month is February 28 (February 29 in a leap year), and January 31 to March 15, 2026 is 1 month and 15 days.
What does the decimal number of months mean?
It is the whole months plus the part of the next month that has passed. From January 15 to September 30, 2026: the last monthly date is September 15, 15 days before the end date, and the next is October 15, 30 days after it, so the answer is 8 + 15 ÷ 30 = 8.5 months.
Why not divide the days by 30 or 30.44?
Because months have 28 to 31 days. Dividing by the length of the actual month means a whole number of months always comes out whole: from November 30, 2025 to February 28, 2026 is exactly 3 months.
How many months ago was a date?
Leave the end date as today and enter the date as the start date. The page reads today’s date from your device when it loads, so the answer is right on the day you open it.
Can the end date be before the start date?
No. If the end date is before the start date there is no answer; swap the two dates.