Date Difference Calculator
Enter a start and end date to find exactly how much time lies between them.
How this calculator works
Pick any two dates — past, present, or future — and this tool works out the precise interval between them: full years, months, and remaining days, plus the total number of calendar days, weeks, and weekdays in that span.
It's useful for anything from planning a project timeline, working out someone's age at a historical event, counting down to a deadline, or figuring out how many working days fall between two dates.
Common questions (FAQs)
Does it matter which date I put first?
No — if the end date comes before the start date, this tool automatically swaps them so you always get a positive result.
What does "weekdays only" mean?
It's the count of days between your two dates that fall on Monday through Friday, excluding Saturdays and Sundays — useful for estimating working days.
Does this account for leap years?
Yes. The calculation is based on real calendar dates, so leap years and varying month lengths are automatically handled.
Is my data stored anywhere?
No — the calculation runs entirely in your browser and nothing is sent to or stored on a server.
Does the calculator include the end date in the total days count?
By default, this calculator calculates the difference (duration) between two dates. It does not count the starting day as an extra full day unless you manually add 1 to the result.
Can I calculate the difference between today and a date in the 22nd century?
Yes. You can enter future calendar dates up to the year 3000 to find durations or plan far-ahead events.
How many weeks are in 100 days?
Dividing 100 days by 7 yields approximately 14.3 weeks. The calculator provides week calculations up to one decimal point.
Why does the week decimal value end in .3 or .6?
Since weeks contain 7 days, decimal values correspond to fractions of 7 (e.g., 2 days is 2/7 or ~0.3 weeks; 5 days is 5/7 or ~0.7 weeks).
Are national holidays excluded from weekdays?
No. "Weekdays only" counts all Mondays through Fridays. Since public and local holidays vary globally, they are not excluded.
What calendar system does this tool use?
This tool utilizes the Standard Gregorian calendar, which is the standard calendar system used globally today.
How do historical calendar shifts (like 1752) affect calculations?
JavaScript Date calculations project the Gregorian calendar retroactively. Therefore, historic calendar adjustment periods (like Julian to Gregorian transitions) are calculated using projected Gregorian rules.
Can I calculate negative intervals?
No. The calculator automatically handles date sorting. If the start date is later than the end date, it silently reverses the inputs to yield a positive duration value.