Days Between Dates Calculator

How the day count is calculated

Each date is converted to a serial day number: the count of days since 1 January 1970 on the Gregorian calendar, the same reference point used by UTC timestamps. The number of days between two dates is then the difference between their serial numbers. Because only whole days are involved, there is no clock time, no time zone and no daylight-saving shift that could turn a 24-hour day into 23 or 25 hours and knock the answer off by one.

days = serial(end) − serial(start)
inclusive count = days + 1

The default leaves out the end date, the way you would say "from Monday to Friday is four days". Switch the option to include it when you are counting every date on a list, such as the days of a hotel stay including checkout or the number of dates in an event that runs Monday through Friday (five).

Worked examples

Example 1: across a leap day

From 2024-02-01 to 2024-03-01: February 2024 has 29 days because 2024 is divisible by 4, so the answer is 29 days, exactly one calendar month. The same dates in 2025 give 28 days.

Example 2: a project deadline

From Monday 2026-01-05 to Friday 2026-03-27 is 81 days, which is 11 weeks and 4 days. Of those 81 days, 59 are weekdays and 22 fall on Saturdays or Sundays. Including the end date adds Friday, making 82 days and 60 weekdays.

Example 3: a whole year

From 2023-07-01 to 2024-07-01 is 366 days because the range contains 29 February 2024. From 2024-07-01 to 2025-07-01 is 365 days. Saying "one year" hides that difference, which matters for daily interest or rental calculations.

How to read the result

The large figure is the total number of calendar days. The sentence underneath restates it as whole weeks plus leftover days, and as a calendar span of years, months and days measured from the start date. The bar splits the period into weekdays (blue) and weekend days (amber), and the table repeats those counts along with the equivalent hours and minutes for a span of whole days.

If the end date is earlier than the start date, the calculator counts backwards and says so, so you can type the dates in either order. The weekday figure counts Monday through Friday only; it does not know about public holidays, company shutdowns or regional observances.

Inclusive or exclusive: which is right?

There is no universal rule, which is why the option exists. Elapsed-time questions — how long until a holiday, how old an invoice is, how many days a loan has been outstanding — normally exclude one end. Counting questions — how many days a festival runs, how many nights plus the departure day you need meals for, how many dates are on a rota — normally include both ends. Legal and contractual deadlines often have their own written rule, for example "within 30 days after receipt" usually starts counting the day after receipt. When money or a legal right depends on the answer, read the agreement's definition of the period.

Calendar months versus days

The years-months-days span measures from the start date's day number. 31 January to 28 February counts as 28 days, which the calendar breakdown shows as 0 months and 28 days, because 31 February does not exist. Spans that end on an earlier day of the month borrow the month before the end date; if the start day is past that month's last day, the whole borrowed month counts and only the end month's days remain. For example, 31 January to 1 March shows 1 month and 1 day (31 days apart in 2026, 30 in a leap year): one full month to the end of February, then one day. This mirrors how people usually describe ages and tenancies and is the same method used by our age calculator. If you need to land on an exact date a number of months away, use the add or subtract days calculator, which clamps to month ends explicitly.

Limits and assumptions

The calculator supports dates from year 1 to 9999 using the proleptic Gregorian calendar, meaning today's leap-year rules are applied to all years, including those before the calendar was adopted in 1582 (or 1752 in Britain and its colonies). Historical documents dated on the Julian calendar need converting before you compare them. Weekend days are fixed as Saturday and Sunday; in countries with a Friday–Saturday weekend, adjust accordingly. Finally, this is a date tool: if you need a duration between two clock times on the same day, subtract the times separately.

Common uses

People use a day counter to plan pregnancies and due dates with their clinician, to check notice periods for tenancies and jobs, to work out the age of an invoice for late-payment terms, to schedule study plans before an exam, to count streaks and habits, and to verify the number of days of daily-rate interest. Travellers use it to stay inside visa limits that are expressed in days within a rolling period, though in that case you should total each stay separately and follow the issuing country's rules. To express a count as a share of a year, divide by 365 or 366 and use the percentage calculator.