How to use the date calculator
Count days between two dates
- Select Days between dates.
- Choose a start date and an end date.
- Tick Include the end date if both the first and last day should count — for example, a vacation from Monday to Friday is 5 days when you include the end date.
- See the total in days, the breakdown in years, months and days, and the number of business days.
Add or subtract time from a date
- Select Add / subtract.
- Pick a start date, choose Add or Subtract, and enter years, months, weeks and/or days.
- The resulting date appears instantly, along with the day of the week.
How days between dates are counted
By default, the calculator counts the number of midnights between the two dates — the same way you would say there is 1 day between today and tomorrow. This is how deadlines, interest periods and "days until" countdowns are usually measured. Turning on Include the end date adds one day, which is how hotel stays, rentals and event durations are often counted.
Examples
- From January 1, 2026 to December 25, 2026 there are 358 days.
- Adding 90 days to March 1, 2026 gives Saturday, May 30, 2026.
- Adding 1 month to January 31 gives February 28 (or 29 in a leap year), because February has no 31st.
Business days
Business days count Monday through Friday and skip weekends. Public holidays vary by country and region, so they are not subtracted automatically — subtract any holidays that fall within your range manually. For example, a span with 22 weekdays that includes one public holiday has 21 working days.
Common uses
- Counting down to a wedding, vacation, exam or birthday.
- Working out deadlines like "30 days from the invoice date" or "90 days from purchase."
- Calculating notice periods, probation periods and contract lengths.
- Finding how many days you have been at a job or in a relationship.
Frequently asked questions
How do I calculate the number of days between two dates?
Enter a start date and an end date in the calculator. It counts the days between them, accounting for different month lengths and leap years. Tick "Include the end date" if you want to count both the first and last days.
Does the calculator include the end date?
By default it does not, which is the standard way to count elapsed days. Tick "Include the end date" to add one day to the total.
How are business days calculated?
Business days are Monday through Friday. The calculator excludes Saturdays and Sundays but does not know about public holidays, so subtract those yourself.
What happens when I add a month to January 31?
The calculator moves to the last valid day of the target month. January 31 plus one month becomes February 28, or February 29 in a leap year.
How many days are in a year?
A common year has 365 days and a leap year has 366. Leap years occur every four years, except years divisible by 100 but not by 400 — so 2000 was a leap year but 1900 was not.
Results are provided for convenience and rounded for display. Sales tax rules, tipping customs and date conventions differ by location, so check local rules when it matters.
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