Date Difference Calculator: Days Between Dates

The total is the number of whole 24-hour days from the start date to the end date, counted in UTC so daylight-saving shifts never add or remove a day. From that total, the other formats are derived.

• Total days: end date − start date. By default the end date itself is not counted, so 1 January to 2 January is 1 day.
• Years, months, days: pure calendar arithmetic. Subtract year from year, month from month, day from day. If the day subtraction goes negative, borrow one month and add that month's length; if the month subtraction goes negative, borrow one year and add 12 months.
• Months, days: the same result with years folded into months (years × 12 + months).
• Weeks, days: whole weeks = total days ÷ 7 rounded down, with the remainder as days.
• Weekdays and weekend days: the calculator walks day by day from the start date, counting Monday–Friday as weekdays and Saturday–Sunday as weekend days.

Sources: the four-format breakdown mirrors calculator.net's Date Duration Calculator; calendar rules follow the proleptic Gregorian calendar described in the month table below.

Take 1 January 2026 to 18 October 2026. The days before October are 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 = 273, plus 17 days of October gives 290 days in total.

Years, months, days: 2026 − 2026 = 0 years; 10 − 1 = 9 months; 18 − 1 = 17 days — so 0 years 9 months 17 days. That is also 9 months 17 days, and 290 ÷ 7 = 41 remainder 3, so 41 weeks 3 days. Walking the 290 days one by one finds 207 weekdays and 83 weekend days (207 + 83 = 290, which checks out).

Pick both dates from the native calendar pickers — typing is allowed too — then press Calculate. The four headline figures appear first, followed by the weekday/weekend breakdown and the two highlighted month calendars.

Step by step

1. Pick the start date. Click the field to open your device's calendar picker, or type the date in YYYY-MM-DD format.
2. Pick the end date. If it falls before the start date, the calculator swaps the two and tells you it did.
3. Decide about the end date. Tick "Include the end date in the count" only when the end day itself should be counted — most durations exclude it.
4. Press Calculate. Read the four formats, the weekday/weekend split and the calendars; use Reset to clear everything.

Months have different lengths, so "9 months 17 days" cannot be converted to an exact number of days — it is a calendar position, not a fixed count. The years–months–days format keeps the answer honest: it tells you where the end date lands on the calendar, while the total-days figure gives you the exact count. That is why the calculator shows both, like calculator.net's date calculator does.

The borrowing rule is the whole trick. When the day of the end date is smaller than the day of the start date, the calculator borrows one month and adds that month's actual length (28, 29, 30 or 31 days) — never an average. This is why 31 January to 1 March is 1 month 1 day in a non-leap year but 1 month 2 days across a leap-year February.

Breakdown formats compared

If the span you care about is a person's age rather than a generic duration, our age calculator is the better fit: it frames the same years–months–days arithmetic around a birth date and a current date.

This calculator uses the Gregorian calendar — the civil calendar used almost everywhere today — for every date it accepts. A year is 365 days, and a leap day is added when the year is divisible by 4, except for century years, which must also be divisible by 400. So 2024 was a leap year, 2000 was a leap year, but 1900 and 2100 are not.

Month lengths

The leap rule matters most around February. 2024-02-28 to 2024-03-01 is 2 days because 29 February 2024 existed; the same dates in 2023 give 1 day. If you want to double-check a result against an independent tool, timeanddate.com's date duration calculator is a solid second opinion.

People reach for a date difference calculator for the spans that matter: how long a project ran, how many days until a deadline, the exact length of a notice period, the gap between two events, or how far apart two birthdays are. The weeks format is handy for schedules, and the total-days figure is what you need when every day counts the same — daily rates, interest, or countdown-style math.

One thing this page deliberately does not do is business-day counting. If you need working days only — excluding weekends and holidays for a contract or a payroll run — use our workdays calculator instead; that tool is built around business days, while this page counts every day on the calendar. And if you want a live ticking counter toward an upcoming event rather than a fixed span, the countdown calculator is the right tool.