To count the days between two dates, add up the days left in the first month, the full months in between, and the days into the last month. From 1 March 2026 to 15 June 2026 that gives 106 days. If you want to include both the start and the end date, add 1, which gives 107. Or skip the arithmetic and use our date duration calculator.
Inclusive or exclusive: decide first
Most mistakes come from counting the wrong way. There are two common conventions:
- Exclusive (the difference). Count the nights, or the steps from one date to the other. Monday to Wednesday is 2 days. This is what calculators, spreadsheets and most contracts mean by “days between”.
- Inclusive. Count every calendar day you touch, including the first and last. Monday to Wednesday is 3 days. Hotel stays are exclusive (2 nights), but a 3-day conference from Monday to Wednesday is inclusive.
The inclusive count is always the exclusive count plus one. When a form, visa or leave policy gives a number of days, check which one it means; if it says “including the day of arrival and departure”, it is inclusive.
Know your month lengths
Thirty days has September, April, June and November. All the rest have 31, except February, which has 28 days, or 29 in a leap year. If you never remember the rhyme, use the knuckle trick.
The knuckle trick
Make a fist and look at your knuckles and the dips between them. Starting from the first knuckle, name the months: January (knuckle), February (dip), March (knuckle), April (dip), May, June, July. July lands on the last knuckle; start again from the first knuckle with August. Every month on a knuckle has 31 days, and every month in a dip has 30, apart from February.
Worked example 1: same year
From 1 March 2026 to 15 June 2026:
- Days left in March after the 1st: 31 − 1 = 30.
- Full months in between: April 30 + May 31 = 61.
- Days into June: 15.
- Total: 30 + 61 + 15 = 106 days (exclusive), or 107 inclusive.
Worked example 2: across a year end
From 20 November 2025 to 5 February 2026:
- Days left in November after the 20th: 30 − 20 = 10.
- December: 31. January: 31.
- Days into February: 5.
- Total: 10 + 31 + 31 + 5 = 77 days.
If February is part of the span, check for a leap year. Any range that includes 29 February 2028 will be one day longer than the same range a year earlier.
Worked example 3: from today
Today is Tuesday, October 6, 2026. Christmas is on Friday, December 25, 2026, which is 80 days away, or 11 weeks and 3 days. Counting from today works the same way: days left this month, plus full months, plus days into the target month. For a live count, see days until 25 December.
Counting backwards: days since a date
To find how many days have passed since a date, swap the order: start at the past date and count forward to today. The same inclusive and exclusive rules apply. Our days since calculator does this for any date, which is handy for streaks, anniversaries and warranty periods.
Shortcuts for long spans
- For whole years, use 365 days per year and add 1 for each 29 February in the range.
- For a span in weeks, divide the days by 7. 106 days is 15 weeks and 1 days.
- For working days, you need a different method; see how to count business days.
- In a spreadsheet, subtracting one date cell from another gives the exclusive count; see Excel and Google Sheets date formulas.
Frequently asked questions
Do you count the first day when counting days between dates?
Usually not. The standard difference counts from the start date to the end date without including the start, so 1 to 3 March is 2 days. Add 1 if you need both dates included.
How many days are there between 1 March and 15 June?
There are 106 days between 1 March and 15 June in any year, or 107 if you count both dates. February is not in the range, so leap years make no difference.
How do I count days between two dates in different years?
Count the days left in the first year, add 365 or 366 for each full year in between, then add the day number of the end date within its year.
What is the quickest way to count days between dates?
Use a calculator such as our date duration tool, or subtract the two dates in a spreadsheet. By hand, add month by month using the knuckle trick for month lengths.