📅 Date Calculator
Calculate the number of days between two dates, or add or subtract days, weeks, months or years from a date.
Days between two dates
Add or subtract from a date
About Date Calculator
This page handles two related but distinct date problems: finding the number of days between two dates, and adding or subtracting a span of time (days, weeks, months, or years) from a starting date. The first is useful for things like counting down to a deadline or figuring out how long a project took; the second is useful for finding a date a fixed distance away, like a due date, renewal date, or anniversary.
Both calculators work on calendar dates using standard date arithmetic, which means they correctly account for varying month lengths and leap years rather than assuming every month has 30 days or every year has exactly 365. Adding months has one edge case worth knowing: if you add a month to a date that doesn't exist in the target month — like January 31 plus one month — the result rolls over based on how many days that month actually has, which can land on a different day than you might expect.
Days between two dates counts full calendar days elapsed — check which convention you need if you're counting inclusively (both the start and end date) versus exclusively, since the two can differ by one day depending on context.
Frequently asked questions
Does this account for leap years?
Yes — all calculations use standard JavaScript date arithmetic, which correctly accounts for leap years and varying month lengths.
Are the start and end dates both counted in "days between"?
The result is the number of full days elapsed between the two dates, which is the same as an exclusive count — the span from a date to itself is 0 days. If you need an inclusive count (both endpoints counted, common for things like "how many days does this event span"), add 1 to the result.
What happens when I add a month to the end of a month, like January 31?
The date rolls over based on the target month's actual length. Adding one month to January 31 lands on March 3 (or March 2 in a leap year) in standard JavaScript date arithmetic, because February doesn't have 31 days and the extra days spill into the next month — worth checking manually if you need the last day of the target month specifically.
Can I subtract time instead of adding it?
Yes — enter a negative number, or use the subtract option if the calculator provides one, to move backward from the starting date by the specified number of days, weeks, months, or years.
Does this account for time zones?
No — calculations are based on calendar dates only, not specific times or time zones. If you need to measure elapsed time down to the hour across time zones, this tool isn't the right fit.