Date & Time
Days Between Dates Calculator
This calculator finds the exact number of days between two dates — useful for deadlines, countdowns, billing periods, or tracking how long something has been (or will be) since a given date.
The formula
days = (end date − start date) ÷ 1 day
Worked example
From March 1, 2026 to March 15, 2026:
days = 14 days (2 weeks, 0 days)
Frequently asked questions
How is the number of days between two dates calculated?
The calculator converts both dates to a single point in time, finds the difference in milliseconds, and divides by the number of milliseconds in a day to get a whole number of days.
Can the end date be before the start date?
Yes — if the end date is earlier than the start date, the result will be negative, showing how many days earlier it is.
Does this count the start or end day itself?
This calculator returns the difference between the two calendar dates (e.g. Jan 1 to Jan 3 is 2 days), not an inclusive day count. If you need an inclusive count, add 1 to the result.