Counting days
By default the end date is not counted — from Monday to Tuesday is 1 day. Tick Include end date to count both days, which is useful for things like the length of an event or a hotel booking counted in days rather than nights.
Business days
Business days count Monday to Friday only. Public holidays vary by country and aren't subtracted, so remove any that apply to you.
Adding months
When adding months lands on a day that doesn't exist (for example, January 31 + 1 month), the result moves to the last day of that month (February 28 or 29).
Worked examples
Days between dates: from March 1 to July 4 in the same year. March has 30 days remaining after the 1st, April 30, May 31, June 30, plus 4 days of July: 30 + 30 + 31 + 30 + 4 = 125 days, or 17 weeks and 6 days.
Adding days: a 90-day warranty that starts on January 15 runs out on April 15 in an ordinary year (16 remaining days of January + 28 of February + 31 of March + 15 of April = 90), and April 14 in a leap year.
Days in each month
| Month | Days | Month | Days |
|---|---|---|---|
| January | 31 | July | 31 |
| February | 28 (29 in a leap year) | August | 31 |
| March | 31 | September | 30 |
| April | 30 | October | 31 |
| May | 31 | November | 30 |
| June | 30 | December | 31 |
Frequently asked questions
Which years are leap years?
A year is a leap year if it divides evenly by 4 — except century years, which must divide by 400. So 2024 and 2028 are leap years, 1900 was not, and 2000 was. The calculator handles this automatically.
How many business days are in a year?
A year has 260 to 262 weekdays, depending on which days of the week it starts and ends on. After subtracting around 10 or 11 public holidays, a typical U.S. working year has about 250 business days.
How do I count "30 days from today"?
Use the second calculator: leave the start date as today, choose Add and enter 30 in the Days box. Note that "30 days" and "one month" are not the same thing — one month from January 31 is the end of February, while 30 days from January 31 is March 2 (or March 1 in a leap year).
Does the count include the start and end dates?
By default it counts the start date but not the end date, which is the usual way to measure a duration: Monday to Friday is 4 days. Choose "Include end date" to count both — Monday to Friday becomes 5 days, which is how you'd count the days of an event or a booking.
How many weeks are in a year?
52 weeks and 1 day (2 days in a leap year). That's why a date falls one weekday later each year, or two after a leap day.