Guides / Dates

How to Count Days Between Two Dates

Counting days sounds simple until you need an exact answer for a contract, a deadline or a visa. A few rules keep the count accurate.

Subtract the dates

The number of days between two dates is the later date minus the earlier date. Calendars store dates as counts of days, so this subtraction is exact. For example, from 1 January to 1 March is 59 days in a non-leap year: 31 days in January, then 28 days in February.

Count inclusively or exclusively

Be clear about whether the start date counts. Most date calculators, including ours, give the gap between the dates. If a notice says "within 30 days of 1 May", the count may include 1 May itself, which makes the deadline one day earlier than a simple subtraction suggests. When the stakes are high, check the wording of the rule or ask the organisation which method it uses.

Leap years

February has 29 days in a leap year. A year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400. So 2024 was a leap year, 2100 will not be, and 2000 was. A calculator handles this automatically, which is one reason to use one rather than counting on your fingers.

Adding and subtracting days

To find a future date, add the number of days to the starting date. To find an earlier one, enter a negative number. Remember that business days, which skip weekends and holidays, are a different calculation and need their own count.

Try it yourself

The Date Calculator shows the days between two dates in days and weeks, and finds the date a set number of days from another, including the day of the week.