Calculate days between dates — and much more
Counting days between two dates sounds trivial until you hit a month boundary, a leap year, or need to exclude weekends. This calculator handles all of it: it shows the gap between any two dates in days, weeks, months, and years simultaneously, counts business days separately, and can add or subtract any combination of years, months, and days from a starting date to find an exact future or past date.
Days between two dates
The most common use: pick a start date and end date, and the calculator shows the total gap in every unit at once. Useful for working out how many days until a deadline, how long since an event, the duration of a project, or the exact gap between two milestones. The result also shows the weekday count separately — Monday through Friday only, no weekends — which is essential for business or legal deadlines.
Add or subtract days, weeks, months, or years
Need to know the date 90 days from today? Or 6 months and 15 days from a contract signing? Switch to Add / subtract mode, enter the start date, and add or subtract any combination of years, months, and days to land on the exact target date. This mode is useful for calculating due dates, subscription renewals, warranty expiry, notice periods, and project timelines.
Common real-world uses
- Project planning — how many days between kickoff and the deadline, excluding weekends
- Legal and contracts — 30-day notice periods, 90-day warranties, lease end dates
- Health and fitness — days into a programme, weeks until a race or event
- Travel — exact number of days in a trip for visa or insurance purposes
- Finance — days between invoice date and payment due date, interest accrual periods
- Countdowns — days until a birthday, wedding, holiday, or retirement
Why date arithmetic is harder than it looks
Months have 28, 29, 30, or 31 days. Leap years add a day in February every four years (with exceptions for century years). Adding one month to January 31st could mean February 28th or March 2nd depending on the rule used. This calculator uses the most widely accepted conventions: months roll to the last valid day of the target month, and leap years are calculated using the Gregorian calendar standard.