Date & Time · 1 min read
How to calculate the days between two dates
Subtract the earlier date from the later one. Leap years and whether you count both end dates are the only details to watch.
Last updated November 5, 2026
Count by hand
Split the span at month ends.
January 15 to March 1, 2026
| Span | Days |
|---|---|
| January 15 to January 31 | 16 |
| January 31 to February 28 | 28 |
| February 28 to March 1 | 1 |
Result: 16 + 28 + 1 = 45 days
Check: January 15 to February 15 is 31 days, and February 15 to March 1 is 14 more days, so 45 again.
Leap years
In a leap year February has 29 days. The same span in 2028 is 46 days.
Important
A year is a leap year when it divides by 4, except century years, which must divide by 400. 2000 was a leap year; 1900 was not.
Include the end date or not
The plain difference counts the nights between the dates, 45 in the example. If you need to count both the first and the last day, for instance days in a rental period, add 1 and get 46.
Tip
State which rule you use, so that other people count the same way.
Convert to weeks
Divide the days by 7. 45 days is 6 weeks and 3 days.
Business days
Calendar days include weekends and holidays. If you need working days, use a business days calculation instead, because the answer is smaller and depends on your holiday calendar.