Date Calculator

Date calculator at a glance#

How many days are between two dates?#

To figure out how many days are between two dates, you subtract the earlier date from the later one, taking into account the actual length of each month in between. For example, from January 20, 2026 to April 10, 2026 is 80 days. When you enter both dates in the Count Days tab, the calculator will also display the gap in months and days, weeks, hours, minutes, and seconds.

How do you add days to a date?#

To add days to a specific date, count forward from the start date, moving into the next month each time you surpass the last day of a month. Adding 80 days to January 20, 2026 will bring you to April 10, 2026, and adding 90 days lands on April 20, 2026. The Add/Subtract tab handles this process for any combination of years, months, weeks, and days.

Does a date calculator count both the start and end date?#

No, it doesn't. The result shows the gap between the two dates by counting the start day and not the end day. If you need both days to count, such as for a hotel stay or an event that continues through its last day, you should add 1 to the result.

What counting the days between dates means#

Calculating the difference in dates involves counting the number of midnights between the two dates. From January 20 to January 21 is 1 day because one midnight occurs between them. The end date isn't counted by itself because it marks the point where counting stops.

The challenge in manual calculations lies in the fact that months have varying lengths. January, March, May, July, August, October, and December each have 31 days, while April, June, September, and November contain 30. February has either 28 days or 29 in a leap year. The example mentioned on this page, January 20, 2026 to April 10, 2026, includes all three types of month lengths.

How to count the days between two dates by hand#

To count days manually, split the span at each month boundary and sum up the segments.

• For days left in the starting month: January has 31 days, so from January 20 to January 31 the calculation is 31 minus 20, which is 11 days.
• Every full month in between: February 2026 has 28 days, and March has 31.
• The day number of the end date: April 10 contributes 10 days.

The total becomes 11 + 28 + 31 + 10 = 80 days. This method applies to any pair of dates in different months. If both dates fall within the same month, simply subtract the day numbers.

For spans covering several years, first count the complete years. A common year has 365 days, and a leap year has 366. Add the days for each full year, then use the month method for any remaining days.

Reading the result in months and days#

While days are precise, people often prefer the answer in months. A month doesn't have a fixed number of days, so the calculator counts whole months first, then the leftover days. From January 20 to February 20 is one month, and to March 20 is two months. Moving from March 20 to April 10 adds another 21 days, so the result is 2 months 21 days.

When the start day falls late in a month, the calculator still counts forward like a calendar, whole months first and then the days left over. From March 28 to May 1, 2026 it shows 1 month 3 days. The total day count, 34 days, is always exact.

The other lines in the result rely on the same 80 days. Dividing by 7 gives 11 weeks and 3 days. In terms of hours, it's 1,920, in minutes 115,200, and in seconds 6,912,000. For periods over a year, the first line breaks the gap into years, months, weeks, and days. A gap of exactly 36 years reads 36 years. Two small calendars below the result mark the start and end dates.

Adding and subtracting days, weeks, months and years#

The Add/Subtract tab begins with one date and moves it forward or backward. Choose Add or Subtract, then enter any of years, months, weeks, and days. Weeks have 7 days each, so 12 weeks after January 20, 2026 is April 14, 2026. To count backward, switch to Subtract: 80 days before April 10, 2026 becomes January 20, 2026, mirroring the forward count.

When dealing with months, pay attention at the month's end. Adding one month to January 31, 2026 asks for February 31, which does not exist. The calculator automatically moves the 3 extra days forward, giving March 3, 2026. Some contracts or billing systems might stop at the month's last day and give February 28. If a deadline relies on that rule, review the agreement's wording.

Years function similarly to months. Adding 1 year to January 20, 2026 gives January 20, 2027. Starting from February 29 in a leap year, adding a year asks for a date that does not exist, so the calculator moves it to March 1.

Inclusive and exclusive counting#

Exclusive counting gives the gap between two dates, which is what the calculator displays: 80 days from January 20 to April 10, 2026. Inclusive counting incorporates both the first and last days, adding one more, making it 81 days.

Use the exclusive figure for a duration, like how long ago an event occurred or time left until a trip. Opt for the inclusive figure when both end days are part of the period, such as festival days or a rental that charges for the return day.

Leap years#

A leap year adds February 29 to the calendar. Under the Gregorian calendar, a year qualifies as a leap year if it's divisible by 4, except century years, which must also divide by 400. So, 2000 was a leap year, while 1900 wasn't. Leap years exist because Earth takes approximately 365 days and 6 hours to orbit the Sun.

The extra day appears in any count crossing February's end. From January 1 to March 1, 2026 is 59 days. From January 1 to March 1, 2028 totals 60 days, since 2028 is a leap year. The calculator accounts for every February 29 in the range.

Holidays, weekends and business days#

Both tabs offer a holidays option. In Count Days, tick Count Holidays and list each holiday by month and day, and the calculator deducts those days from the total. In Add/Subtract, tick Exclude Holidays to skip the listed days, which pushes the result date further from the start.

The calculator includes calendar days, so weekends remain in the count. To calculate weekdays from a day count, use whole weeks. The 80 days from January 20, 2026 are 11 full weeks and 3 additional days. Each complete week includes 5 weekdays, which gives 55, with 3 leftover days falling from Tuesday April 7 to Thursday April 9, all weekdays. That is 58 weekdays before considering holidays.

Where a date calculator helps#

• Deadlines: a 30-day return window, a 90-day notice period, or a set number of days after an invoice for payment.
• Countdowns: calculating the days remaining for a trip, wedding, or exam.
• Looking back: determining how many days ago a project started or a subscription began.
• Planning in weeks: figuring out the date 12 weeks from a start date for a training plan or course.

For an exact age from a date of birth, the age calculator gives years, months and days. For the hours and minutes between two dates and times, use the time duration calculator, and for two clock times on the same day, the hours calculator.

Dates before and after January 20, 2026#

Here are common offsets from the example start date, worked out the same way as the Add/Subtract tab. Three months and 90 days land on the same date here, but that only happens when the months in between add up to exactly 90 days.

Sources#

• Hong Kong Observatory, Leap Year (the Gregorian leap year rule)
• NASA Space Place, What Is a Leap Year?

Frequently asked questions#

How many weeks are between two dates?#

Count the days, then divide by 7. The 80 days from January 20 to April 10, 2026 convert to 11 weeks and 3 days. The calculator displays this line under the day count, so manual division isn't necessary.

How many months are between two dates?#

Count full calendar months from the start date, then tally the remaining days. From January 20 to April 10, 2026 is 2 months and 21 days. Since months range from 28 to 31 days, the answer is given as whole months plus any days left over, never as a decimal.

Does the date calculator skip weekends?#

No, it counts calendar days, incorporating Saturdays and Sundays. You may list holidays to exclude, and for weekdays only, multiply the full weeks by 5 and examine the leftover days on a calendar.

Can I count backward from a date?#

Yes, in the Add/Subtract tab, choose Subtract, then enter the years, months, weeks, or days to subtract. 80 days before April 10, 2026 is January 20, 2026, and 6 months before January 20, 2026 leads to July 20, 2025.

How many days are in a year?#

A common year consists of 365 days, whereas a leap year contains 366. Specifically, 2026 and 2027 have 365 days each, and 2028 is the next leap year with 366 days.

Why is adding one month to January 31 not February 28?#

February lacks a 31st, so the date has to shift. The calculator above carries the extra days into March, resulting in March 3 for 2026 and March 2 in a leap year like 2024. Other tools might stop at February's end, so verify your deadline's rule.