How to use the date calculator
Choose Days between dates to measure a period, or Add or subtract to find a date before or after another one. Results update as you type.
Days between two dates
- Enter the Start date and the End date. The end date starts on today; the Today buttons put either field back to the current date.
- Tick Include the end date (+1 day) if both the first and the last day should count, for example for a holiday booking or a number of days of leave.
- Read the total in days, then the same period in weeks and days, months and days, years, months and days, business days, weekend days and hours. Each date is shown with its day of the week.
- Optionally open Exclude holidays from business days and list the holiday dates that apply to you.
Add or subtract days, weeks, months or years
- Enter the Start date and choose Add or Subtract.
- Fill in any mix of Years, Months, Weeks and Days, or use a quick button such as +30 days or +6 months.
- Tick Business days only to count the Days box in weekdays (Monday to Friday).
- Read the result date with its weekday and ISO format (YYYY-MM-DD), and how many calendar days it is from the start date.
How the days are counted
The day count is the difference between the two dates: the start date is counted and the end date is not. From 1 January to 31 January is 30 days, the same way that from Monday to Tuesday is one day. If you tick Include the end date, both ends count and the answer is 31 days. Use the inclusive count when every listed day matters, such as hotel nights versus days of a festival, a period of leave, or a stay that counts both the arrival and the departure day.
The calculator works on whole calendar dates, not on clock time, so changes between summer and winter time never shift the result: from 28 March 2026 to 30 March 2026 is 2 days, even though the clocks go forward in between in many countries. Hours and minutes are simply the days multiplied by 24 and by 1,440.
Months, years and the month-end rule
Months have 28 to 31 days, so "one month" depends on where you start. This calculator uses the same calendar rule as our age calculator: a month after a date is the same day number in the next month, and if that day does not exist, the last day of that month is used. So 31 January 2024 + 1 month is 29 February 2024 (a leap year), 31 January 2023 + 1 month is 28 February 2023, and 29 February 2024 + 1 year is 28 February 2025. When you combine amounts, years and months are applied first, then weeks and days.
For "months and days" between two dates, the calculator counts the full months from the start date with that rule, then the days left over. From 29 February 2020 to 28 February 2021 is therefore 1 year, 0 months and 0 days (365 days), because the anniversary of 29 February falls on 28 February in a year without a leap day.
Leap years
The calculator follows the Gregorian calendar. 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 2024 and 2000 were leap years, while 1900 was not and 2100 will not be. Dates from year 1 to 9999 are supported; dates before the calendar was introduced in 1582 use the same rules extended backwards (the proleptic Gregorian calendar), and countries adopted it at different times, Britain and its colonies in 1752. For historical dates written in the older Julian calendar, the result can differ by several days.
Business days and holidays
Business days are Monday to Friday. They are counted over the same days as the total: the start date and every day up to, but not including, the end date, or including it when the end date box is ticked. Monday 5 October 2026 to Friday 16 October 2026 is 9 business days, or 10 with the end date included. Public holidays differ by country and region, so the calculator never removes them on its own; list them under Exclude holidays from business days to subtract the ones on weekdays. When adding business days, the calculator steps forward one weekday at a time like the WORKDAY function in spreadsheets: Friday + 1 business day is Monday.
Examples
| Calculation | Result |
|---|---|
| 1 January 2024 to 31 December 2024 | 365 days (366 with the end date), 52 weeks and 1 day |
| 1 January to 31 January | 30 days (31 with the end date) |
| 31 January 2024 + 1 month | Thursday, 29 February 2024 |
| 31 January 2023 + 1 month | Tuesday, 28 February 2023 |
| 29 February 2024 + 1 year | Friday, 28 February 2025 |
| 1 March 2024 − 1 day | Thursday, 29 February 2024 |
| 28 February 1900 + 1 day | 1 March 1900 (1900 was not a leap year) |
| Monday 5 to Friday 16 October 2026, business days | 9, or 10 with the end date |
What people use it for
- Deadlines and notice periods: 30 days from an invoice date, a three-month notice period, or 14 days to return an order. Contracts define how they count (calendar or business days, inclusive or not), so check the wording.
- Travel rules: some visa and residence rules limit stays, such as the Schengen area's 90 days in any 180-day period, which counts both the entry and the exit day. Use the inclusive count and confirm the rules with an official source.
- Projects and plans: working days to a launch date, weeks until an exam, or how many weeks are left in the year.
- Personal dates: days until a wedding or a holiday, or what day of the week a date falls on. For an exact age from a date of birth, use the age calculator, and for pregnancy and other medical dates ask your midwife or doctor.
To count down to a moment in real time, use the online timer. To write a date in Roman numerals, for an engraving or a tattoo, use the Roman numerals converter. To convert a time between cities, use the time zone converter. More calculators are in everyday tools.
Privacy: all calculations run in your browser and no dates are sent to a server. The only thing stored on your device is which of the two modes you used last, so the page opens on it next time.
Frequently asked questions
How many days are there between two dates?
Subtract the earlier date from the later one in calendar days: enter both dates above and read the total. The count includes the start date but not the end date, so 1 to 31 January is 30 days. Tick "Include the end date" to count both, which gives 31.
Does the date calculator include the end date?
Not by default. Like most date difference calculations, it counts the days from the start date up to the end date. The "Include the end date (+1 day)" option adds the last day, and the weeks, months and business days follow the same choice.
How do I count business days between two dates?
Enter the dates in "Days between dates" and read Business days: it counts Monday to Friday and leaves out Saturdays and Sundays. Public holidays are not removed automatically; list them under "Exclude holidays from business days" to subtract them.
What is 31 January plus one month?
The last day of February: 29 February 2024 in a leap year and 28 February in other years. When the same day number does not exist in the target month, the calculator uses the last day of that month.
How many weeks are there between two dates?
Divide the number of days by 7. The calculator shows it as whole weeks plus the remaining days: 1 January to 31 December 2024 is 365 days, which is 52 weeks and 1 day.
What day of the week was a date?
Every date the calculator shows comes with its weekday. Enter the date as the start or end date and it appears in the result, for example 15 October 2026 is a Thursday.
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