Time & Date

Date Calculator

Count the days between two dates, including weeks, months and weekdays, or add and subtract days, weeks, months and years from a date. Leap years and month ends are handled for you.

Your dates

Days betweenAdd / SubtractBusiness days

Total days

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Weeks and days

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Months and days

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Years, months, days

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Business days (Mon–Fri)

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— weekend days; holidays not removed

Show the math

Days = end date − start date (+1 if the end date is included)

Dates follow the Gregorian calendar. Business-day results skip weekends only; check public holidays and any rules that apply to your deadline.

How days between dates are counted

The date calculator converts each date to a day number and subtracts. By default the start date counts and the end date doesn't, the same way you measure elapsed time: from Monday to Tuesday is one day. Tick Include end date when you need both ends counted, for example the length of a hotel booking you pay per night versus the number of days a festival runs. That option always adds exactly one day.

The breakdowns use the same span. Weeks and days divides the total by 7. Months and days counts how many whole calendar months fit after the start date, then counts the remaining days. Years, months, days groups those months into years. Because months have different lengths, "1 month" can be 28, 29, 30 or 31 days. That's why the month figure can't be converted back to days with a fixed multiplier.

Worked example: from March 15, 2025 to November 2, 2025 is 232 days. That's 33 weeks and 1 day, or 7 months and 18 days (March 15 → October 15 is seven whole months, then 18 more days to November 2). Of those 232 days, 165 fall Monday to Friday. If you want an age in years from a date of birth, the Age Calculator is built for that and also shows your next birthday.

Adding and subtracting days, weeks, months and years

Days and weeks are exact: a week is always 7 days, so adding 2 weeks and 3 days moves the date forward 17 days, across month and year boundaries as needed. Months and years are calendar units, so the calculator keeps the day of the month and changes the month (or year). Adding 3 months to April 10 gives July 10, whether the months in between have 30 or 31 days.

Month-end rule: when the target month is too short for the starting day, the result is the last day of that month. January 31 plus one month is February 28 (or February 29 in a leap year), and February 29, 2024 plus one year is February 28, 2025. The results panel flags it when this happens. Years and months are applied first, then weeks and days, so "1 month and 1 day after January 31, 2025" is February 28 + 1 day = March 1. Spreadsheet functions such as EDATE apply the same clamp.

Subtracting works the same way in reverse. Six months before August 31 is the last day of February, not "February 31" or March 3. For a pregnancy timeline, which counts 280 days from the first day of the last period, use the Due Date Calculator rather than adding 9 months by hand: 9 calendar months is only 273 to 276 days.

Business days, weekends and public holidays

Business days here means Monday through Friday. In the Days between mode they are counted over the same days as the total, so with the end date excluded, Friday to the following Monday is 1 business day (the Friday). The Business days mode moves forward or back a set number of weekdays from a start date, treating the start as day 0. One business day after Friday is Monday, and a Saturday or Sunday start behaves like the Friday before it.

Public holidays are not removed, because they depend on your country, state and employer. In the US there are 11 federal holidays: New Year's Day, Martin Luther King Jr. Day, Washington's Birthday, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving and Christmas. When one falls on a Saturday, most federal employees get the Friday before off; a Sunday holiday moves to Monday (for example, July 4, 2026 is a Saturday, so it is observed on Friday, July 3). Banks, courts and private employers don't all follow the same list, so subtract any holidays in your range by hand.

A full calendar year has 260, 261 or 262 weekdays depending on which weekday January 1 falls on and whether it's a leap year: 2025 has 261 and 2024 had 262. Take off 11 federal holidays and a typical US working year is about 250 days. For hours rather than days, the Hours Calculator adds up shifts and weekly time cards.

Month lengths and leap years

A year has 365 days, or 366 in a leap year. Under the Gregorian calendar a year is a leap year if it divides by 4, except century years, which must also divide by 400. So 2024 and 2000 were leap years, while 1900 was not, and 2100 won't be. The table shows each month's length and the day-of-year number of its last day, which is handy for quick mental checks ("June 30 is day 181, so there are 184 days left in the year").

Month	Days	Last day = day of year (common)	(leap year)
January	31	31	31
February	28 (29 in leap years)	59	60
March	31	90	91
April	30	120	121
May	31	151	152
June	30	181	182
July	31	212	213
August	31	243	244
September	30	273	274
October	31	304	305
November	30	334	335
December	31	365	366

The knuckle mnemonic still works: count months across your knuckles and the gaps between them. Months on a knuckle have 31 days and months in a gap have 30, apart from February. July and August are both 31 because you restart on the first knuckle.

Time zones, daylight saving and why the count doesn't drift

A common bug in home-made date spreadsheets and scripts is subtracting two timestamps, dividing by 24 hours and rounding down. In regions that use daylight saving time, the day the clocks spring forward is only 23 hours long. A span that crosses it comes out a fraction short of a whole day, and rounding down loses a day. This calculator works on calendar dates only, anchored to UTC midnight, so every day is exactly one day long and the result is the same wherever you are.

Time zones matter when an event spans a date line. A flight that leaves Los Angeles late on Monday lands in Sydney on Wednesday local time. Count the days in the time zone where the deadline or contract applies. "Today" in the date fields comes from your device's local date, not UTC, so the default doesn't jump to tomorrow in the evening in the Americas.

Frequently asked questions

How many days are left until the end of the year?

Put today's date as the start and December 31 as the end, then turn on "Include end date" so New Year's Eve itself is counted. On October 10 in a common year the answer is 83 days including both today and December 31, or 82 if you only want the days after today. The weekday count underneath tells you how many of those fall Monday to Friday.

Is 30 days from today the same as one month from today?

Only sometimes. A month is 28 to 31 days long, so "one month" from January 15 is February 15 (31 days later), but from February 15 it is March 15 (28 days later in a common year). Contracts and notice periods usually say which one they mean. If a document says "30 days", add days; if it says "one month", add a month.

What date is 6 months before a given date?

Choose Add / Subtract, switch to Subtract and enter 6 in the months field. The calculator moves back six calendar months and keeps the same day of the month, so August 20 becomes February 20. If that day doesn't exist in the earlier month, as with August 31, it uses the last day of that month instead: February 28, or February 29 in a leap year.

Does "within 10 business days" include the day the request was made?

Usually not. Most deadlines start counting on the next business day, which is how the Business days mode works: the start date is day 0, so 10 business days after a Monday is the Monday two weeks later. Check the wording of the rule or contract, because some count "calendar days" instead and some exclude public holidays as well as weekends.

How do I count the number of weeks between two dates?

Enter both dates in the Days between mode and read the "Weeks and days" result. It divides the total number of days by 7, so 100 days shows as 14 weeks and 2 days. For pregnancy weeks, which are counted from the first day of the last period rather than between two arbitrary dates, the Due Date Calculator applies that convention for you.