Date Calculator
Days Between Two Dates
Press Calculate to see the results.
Add to or Subtract from a Date
Move forward or back from any date by years, months, weeks and days. Months are applied on the calendar, so January 31 plus one month is the last day of February. Choose business days to skip weekends.
Press Calculate to see the results.
Use this date calculator to count the days between two dates, or to find the date a given number of days, weeks, months or years before or after another date. Business-day options skip weekends.
The days-between calculator counts the start date but not the end date, which answers questions like how many nights a trip lasts or how many days remain until an event. Turn on Include end day when both dates should count, such as a contract running from June 1 through June 30 (30 days rather than 29). Results also appear in years, months and days, in weeks, and as business days. Counting from Monday, March 2, 2026 to Monday, March 16, 2026 gives 14 days, 10 of them business days.
History of the Gregorian Calendar
The calendar most of the world uses today is the Gregorian calendar, introduced in 1582 by Pope Gregory XIII. It replaced the Julian calendar, which Julius Caesar had established in 46 BC. The Julian year averaged 365.25 days, about 11 minutes longer than the solar year, and over the centuries that small error had pushed the calendar about ten days out of step with the seasons, moving the date of the spring equinox and therefore of Easter.
The reform fixed this in two ways. First, ten days were dropped at once: in the countries that adopted it immediately, Thursday, October 4, 1582 was followed by Friday, October 15. Second, the leap-year rule was refined. A year is a leap year if it is divisible by 4, except century years, which are leap years only if divisible by 400. So 1900 was not a leap year, but 2000 was. This makes the average year 365.2425 days, within about 26 seconds of the solar year.
Adoption was gradual. Catholic countries such as Spain, Portugal and the Italian states switched in 1582. Britain and its colonies, including those in America, waited until 1752, by which time 11 days had to be skipped: September 2 was followed by September 14. Russia adopted the Gregorian calendar only in 1918 and Greece in 1923. Because of these changes, historical dates can differ depending on which calendar a source used.
Holidays
Holidays often fall on fixed dates or on rules such as the third Monday of a month, so they move around the week from year to year. These are the US federal holidays observed by federal employees and many businesses. When a fixed-date holiday falls on a Saturday it is usually observed on the Friday before, and on a Sunday the Monday after.
| Holiday | Date |
|---|---|
| New Year's Day | January 1 |
| Birthday of Martin Luther King Jr. | Third Monday in January |
| Washington's Birthday (Presidents' Day) | Third Monday in February |
| Memorial Day | Last Monday in May |
| Juneteenth National Independence Day | June 19 |
| Independence Day | July 4 |
| Labor Day | First Monday in September |
| Columbus Day / Indigenous Peoples' Day | Second Monday in October |
| Veterans Day | November 11 |
| Thanksgiving Day | Fourth Thursday in November |
| Christmas Day | December 25 |
Frequently asked questions
How do I count the days between two dates?
Enter the start and end dates. The calculator subtracts them on the calendar; turn on Include end day if both dates should be counted.
How many business days are between two dates?
The calculator counts Monday through Friday in the range. Public holidays are not removed automatically, so subtract any that fall between the dates.
What date is 90 days from today?
Switch to Add or subtract, leave the start date as today and enter 90 in Days. The resulting date appears instantly.
What happens when I add a month to January 31?
The result is the last day of February, February 28 or 29 in a leap year, because February has no 31st.
Why does the Gregorian calendar skip some leap years?
Century years are leap years only if divisible by 400. This keeps the calendar aligned with the solar year, which is slightly shorter than 365.25 days.
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