Date Calculator
Count the days between two dates, add or subtract time from a date, work with business days and US federal holidays, or see how far away any date is.
How the date calculator works
Every date is converted to a whole number of days, so leap years and months of different lengths are handled for you. The difference between two dates is the number of midnights between them. From March 1 to March 10 there are 9 days, or 10 days if you count both the first and the last day.
Besides the total number of days, the calculator breaks the gap into years, months and days, weeks and days, and hours, minutes and seconds. It also counts business days and weekend days, so you can see how much working time is in a period.
Adding and subtracting time
When you add months or years, the day of the month is kept when possible. Adding one month to January 31 gives the last day of February, because February has no 31st. Weeks and days are added after the months and years, as exact day counts.
For every result date you also get the weekday, the day of the year, the ISO week number and how far it is from today. This is handy for planning deadlines, billing dates, probation periods and notice periods.
Business days and US federal holidays
Business days are Monday through Friday. Tick the holiday option to also skip the 11 US federal holidays. When a fixed-date holiday falls on a Saturday it is observed on the Friday before, and when it falls on a Sunday it is observed on the Monday after.
| Holiday | Date rule |
|---|---|
| New Year's Day | January 1 |
| Martin Luther King Jr. Day | Third Monday in January |
| Presidents' Day | Third Monday in February |
| Memorial Day | Last Monday in May |
| Juneteenth | June 19 (since 2021) |
| Independence Day | July 4 |
| Labor Day | First Monday in September |
| Columbus Day | Second Monday in October |
| Veterans Day | November 11 |
| Thanksgiving Day | Fourth Thursday in November |
| Christmas Day | December 25 |
Banks, courts, shipping carriers and employers do not all follow the same calendar, and state holidays are not included. Check your own contract or policy when an exact legal deadline matters.
Worked examples
- Net 30 invoice: an invoice dated October 14 is due 30 days later, on November 13.
- 90-day probation: a start date of January 6 plus 90 days is April 6.
- 10 business days: adding 10 business days to Friday, June 27, 2025 skips two weekends and lands on Friday, July 11 (or Monday, July 14 if July 4 counts as a holiday that week).
- Age in days: pick your birth date as the start date and today as the end date to see how many days you have been alive.
Tips for accurate results
- Decide whether the first and last day both count. Hotel stays and rentals usually count both days, while deadlines usually do not.
- Use the business day tab for delivery windows and notice periods written in working days.
- For long periods, use the years, months and days breakdown rather than dividing days by 30 or 365.
Frequently asked questions
How many days are between two dates?
Choose both dates and press Calculate. The result is the number of days from the start date up to, but not including, the end date, unless you tick the option to include the end day.
Should I include the end day?
Include it when both the first and last day count, such as a hotel stay or a leave request. Leave it off when you want elapsed time, such as the days remaining until a deadline.
Does it handle leap years?
Yes. February 29 is counted in leap years, and the year, month and day breakdown follows the real calendar.
How do I find a date 90 days from today?
Open the Add or subtract tab, press the Today button on the start date, choose Add, enter 90 in the days box and press Calculate.
How are business days counted?
Saturdays and Sundays are skipped. If you tick the holiday option, US federal holidays on weekdays are skipped too, using their observed dates.
What is an ISO week number?
It is the standard week number used in business and logistics. Weeks start on Monday, and week 1 is the week that contains the first Thursday of the year.
How many days are left until a date?
Use the Days from today tab. It shows the days remaining, or the days that have passed, along with the weeks, hours and the weekday of that date.