This site provides an online date calculator to help you find the difference in the number of days between any two calendar dates. Simply enter the start and end date to calculate the duration of any event. You can also use this tool to determine how many days have passed since your birthday, or measure the amount of time until your baby's due date. The calculations use the Gregorian calendar, which was created in 1582 and later adopted in 1752 by Britain and the eastern part of what is now the United States. For best results, use dates after 1752 or verify any data if you are doing genealogy research. Historical calendars have many variations, including the ancient Roman calendar and the Julian calendar. Leap years are used to match the calendar year with the astronomical year.

Note: If you're trying to figure out the date that occurs in X days from today, switch to the Days From Now calculator instead. Or to calculate the date that is X days from a particular date, use the Days From Date calculator. Finally, if you want to choose a day in the week and count how many times it occurs in a given year, try out the How Many Days calculator.


›› Enter dates

Enter two dates below to find the number of days between them. For best results, avoid entering years before 1753. Examples include 1990-02-14 or Jun 4, 1978. You can also type words like today or yesterday, or use the American format, 9/28/2021.

Number of days between:
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›› September, 2021 calendar

Su M Tu W Th F Sa
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Today is Tuesday, September 28th, 2021. It is the 271st day of the year, and in the 39th week of the year (assuming each week starts on a Monday). There are 30 days in this month. 2021 is not a leap year, so there are 365 days in this year.


›› Date calculator

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