How to calculate days between dates

6 October 2026 · Calcosmo editorial team

The number of days between two dates is the difference in days, not counting the end date. From 1 January to 6 October 2026 is 278 days; counting both days, it is 279. Get the answer for any two dates with the days between dates calculator.

Include the end date or not?

This is the most important choice, and it depends on what you need:

• Difference (default): Monday to Wednesday is 2 days. Use this for durations, deadlines, interest periods and age in days.
• Inclusive: a holiday from Monday through Wednesday lasts 3 days. Use this for events, leave days or anything where both the first and last day count.

Hotel stays use the difference: Monday to Wednesday is 2 nights.

By hand in three steps

Example: 14 March 2026 to 6 October 2026.

1. Rest of the start month: March has 31 days, so 31 − 14 = 17 days.
2. Full months in between: April 30, May 31, June 30, July 31, August 31, September 30 = 183 days.
3. Days in the end month: 6.

Total: 17 + 183 + 6 = 206 days, which is 29 weeks and 3 days.

To remember month lengths, use the knuckle trick: make two fists and count the months across your knuckles and the gaps between them. Knuckles are 31 days, gaps are 30 (or 28/29 for February). July and August are both knuckles.

Leap years

If 29 February falls between your dates, add a day. A year is a leap year if it is divisible by 4, except century years that are not divisible by 400. So 2028 is a leap year, 2100 is not, and 2000 was. From 1 January 2028 to 1 January 2029 is 366 days.

Days, weeks, months or business days

• Weeks: divide by 7. 206 days = 29 weeks and 3 days.
• Months: count whole calendar months. 14 March to 6 October is 6 months and 22 days. Because months differ in length, "days ÷ 30" is only an approximation.
• Business days: Monday to Friday, excluding public holidays. The calculator shows weekdays; for public holidays use the working days calculator.

In Excel and Google Sheets

Note that NETWORKDAYS counts both the start and end date if they are weekdays.

Common uses

• Payment terms: an invoice dated 6 October with 30-day terms is due on 5 November.
• Notice periods and probation: check whether the contract says days or calendar months.
• Pregnancy and age: the due date calculator and age calculator work with days between dates too.
• Interest: savings and loan interest is often calculated per day on the number of days the money was held.