Date Calculator
This free date calculator answers two common questions: how many days, weeks, and years are between two dates, and what date you get by adding or subtracting a number of days from a date. Nothing you enter is sent anywhere or stored.
How to Use It
- Days Between Two Dates: pick a start and end date to see the days, weeks, and years between them.
- Add or Subtract Duration: pick a date, choose Add or Subtract, enter a duration, and pick its unit (Days, Weeks, Months, or Years).
- Both update instantly as you change any field.
How It Works
The days-between calculation uses calendar-aware math, not just a division of total days. It accounts for actual month lengths and leap years to produce a correct years/months/days breakdown, the same logic used by the Age Calculator, alongside the raw total-days and total-weeks counts.
The add/subtract calculation always moves from midnight UTC, so daylight saving time changes in your local time zone don't shift the result by an hour. The answer is always a clean calendar date. Days and weeks are added as a fixed number of days. Months and years move by whole calendar months, so if the day of the month you started from doesn't exist in the resulting month, the result lands on that month's last day instead (for example, adding one month to January 31 gives February 28 or 29, not a date pushed into March).
A worked example: January 15, 2026 to July 27, 2026 comes out to 6 months and 12 days apart, 193 total days, or 27 full weeks. Separately, adding 90 days (not months) to January 1, 2026 lands on April 1, 2026, a fixed day-count addition, unlike the calendar-month addition described above, which is why the two operations can land on different dates for what sounds like a similar duration.
Everything runs client-side in your browser. No dates you enter are sent anywhere or stored.
Frequently Asked Questions
How are leap years handled?
Leap years are accounted for automatically. February 29 only appears as a valid day in a leap year, and the total-days count between any two dates correctly includes every leap day that falls within that range, no manual adjustment needed.
How is this different from the Age Calculator?
The Age Calculator answers one specific question: how old someone is from a birthdate, including a countdown to their next birthday. This tool handles general date math between any two arbitrary dates, or adding or subtracting a duration from a date, without any birthday-specific framing. If you're calculating someone's age, the Age Calculator is the more direct tool. For everything else (days until an event, a deadline, a project length), this is the one.
What calendar does the day-of-week calculation use?
The standard Gregorian calendar, the one in everyday use today. It isn't adjusted for dates before the Gregorian calendar's adoption in different countries (which happened at different times, historically), so very old dates may not match historical records exactly.
What happens if a month or year addition lands on a day that doesn't exist?
If adding months or years moves you to a date that doesn't exist in the target month, the result lands on that month's last valid day instead. For example, adding one month to January 31 gives February 28 in a regular year or February 29 in a leap year, rather than spilling over into March. The same rule applies going backward, and to year additions that cross a leap day.
Does adding "1 month" always land on the same day of the month?
Usually, but not always: only when the target month has at least as many days as the one you started from. Adding 1 month to January 15 gives February 15, and adding 1 month to January 31 gives February 28 (or 29), for the reason described above. This differs from adding 30 days, which always moves by a fixed number of days regardless of month length, so "add 1 month" and "add 30 days" from the same date can land on different results.
Can I use this to count down to a deadline or event?
Yes, enter today's date as the start date and the deadline as the end date in the "Days Between Two Dates" panel, and the total-days figure is exactly how many days remain (or have passed, if the deadline is in the past).
Does the days-between count include both the start and end date?
No, it counts the number of days elapsed between the two dates, not the number of calendar dates touched. January 1 to January 2 is 1 day between them, not 2. This matches how "days until" or "days since" is conventionally understood.