A worked example
From January 1, 2026 to December 31, 2026, inclusive of both dates, is exactly 365 days — 2026 is not a leap year.
Frequently asked questions
When should I include both endpoints versus not?
Counting nights for a hotel stay or trip usually means NOT including both dates as full days — checking in on day 1 and out on day 5 is 4 nights. Counting total calendar days something spans (like a project timeline) usually means including both endpoints.
How is this different from the Date Calculator?
This is a deliberately simpler, single-purpose version that only returns a day count — the Date Calculator additionally breaks the difference down into years, months, and days.