Start date, End date, Include the end date
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How this calculator works
The calculator counts calendar days from the start date to the end date and also expresses the gap as whole years, months and days. The end date itself is not counted unless you choose to include it, which matters when you are counting the days of a stay, a project or a rental period.
Formula
- Days = end date − start date
- Including the end date adds 1 day
- Years, months and days are counted calendar-wise from the start date
Worked example
January 1 to December 25, 2026
- Start date
- 2026-01-01
- End date
- 2026-12-25
- Include the end date
- No
Result358 days
From Thursday, January 1, 2026 to Friday, December 25, 2026.
Frequently asked questions
Does the count include the end date?
By default no: January 1 to January 2 is 1 day. Turn on the option to count both the first and last day, which gives 2.
How are months counted when they have different lengths?
Months are counted calendar-wise. January 31 to February 28 is 0 months and 28 days; January 31 to March 31 is exactly 2 months.
Are leap years handled?
Yes. February 29 is included in leap years, following the Gregorian calendar rules.
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Results are estimates based on the values you enter and the published method shown above. They do not replace professional medical, financial or legal advice. Method reviewed October 7, 2026. About this site