Days Between Dates Calculator

How to use the days between dates calculator

Choose a start date and an end date. The calculator immediately shows the number of days between them, the same span in weeks and in years, months and days, plus how many of those days are weekdays (Monday to Friday) and how many fall on a weekend. A table breaks the total down by day of the week — handy if you need to know, say, how many Wednesdays a course runs or how many Saturdays a shop will be open.

Tick Include the end date when both the first and last day should count, such as a hotel stay measured in days, a holiday booking, a conference, or a "from–to" period on a form. Leave it unticked for a simple difference, which is what you want for countdowns ("how many days until…") and for most interest and notice-period calculations.

The formula

The number of days between two dates is the difference between their positions on the calendar:

Internally, each date is converted into a day count (similar to the Julian Day Number used by astronomers), and the two counts are subtracted. This automatically accounts for months of different lengths and for leap years, which add 29 February every four years except in century years not divisible by 400 (2000 was a leap year, 2100 will not be).

Weekdays are counted by noting that every full block of 7 days contains exactly 5 weekdays and 2 weekend days. Only the leftover 0–6 days need to be checked individually.

Worked example

How many days are there from 1 January 2026 to 1 July 2026? January has 31 days, February 28, March 31, April 30, May 31 and June 30 — a total of 181 days, or 25 weeks and 6 days. The start date, 1 January 2026, is a Thursday. The 25 full weeks contain 125 weekdays; the remaining 6 days run Thursday to Tuesday and include 4 weekdays, giving 129 weekdays and 52 weekend days. If you include the end date (Wednesday 1 July), the total becomes 182 days and 130 weekdays.

Inclusive vs exclusive counting

A frequent source of "off by one" mistakes is whether to count the end date. Consider a hotel booking from Monday to Friday: you stay 4 nights (exclusive count) but are on the trip for 5 days (inclusive count). Similarly, a rental from the 1st to the 10th is often billed as 10 days, while the gap between the 1st and the 10th is only 9 days.

• Exclusive (default): countdowns, ages, durations, interest periods.
• Inclusive: events, leave requests, attendance, project calendars, "from and including / to and including" ranges.

Practical uses

People use day counts to plan pregnancy milestones, track how long they have been sober or smoke-free, calculate notice periods, work out pro-rated rent or salary, measure loan interest periods (see our simple interest calculator), check visa limits such as the Schengen 90/180-day rule, and count down to weddings, exams and holidays.

If you need to move forward or backward from a date instead — for instance "what date is 45 business days from now?" — use the date calculator. For someone's exact age, try the age calculator, and for the number of hours worked across a week, the hours calculator.

Days between dates in other units

To turn days into other units, divide by 7 for weeks, by about 30.44 for average months, or by 365.25 for years. The years, months and days figure shown above is more precise: it counts whole calendar months first, so the result matches how people naturally describe durations ("2 months and 3 days").