Date Calculator — Days Between Dates
Our free date calculator computes the exact difference between any two dates in days, weeks, months, and years. Need to know how many business days until a deadline? Toggle the business days option to exclude weekends automatically. The add/subtract mode lets you find a date by adding or subtracting a specific number of days, weeks, or months from any starting date — perfect for calculating due dates, project timelines, and delivery estimates.
Month arithmetic is the part that quietly produces wrong answers elsewhere. Adding one month to 31 January has no correct answer, and different systems give 28 February, 2 March, or an error. This calculator clamps to the last valid day of the target month, which is the convention contracts and billing systems use. The business-day mode excludes weekends but not public holidays, since those vary by country and often by region, so check a local calendar before treating a business-day result as a legal deadline.
How to use Date Calculator
- Select "Days Between" mode and enter two dates to see the difference.
- Toggle "Business days only" to exclude weekends from the count.
- Switch to "Add/Subtract Days" mode to find a future or past date.
- Enter a start date and the number of days/weeks/months to add or subtract.
Features
- Days between two dates — Exact difference in days, weeks, months, and years.
- Add/subtract days — Find a future or past date from any starting point.
- Business days mode — Excludes weekends from the count.
- US holiday exclusion — Optionally exclude US federal holidays.
- Multiple units simultaneously — See results in days, weeks, months, and years at once.
- Leap year aware — Handles all month-length variations correctly.
Frequently Asked Questions
How do I calculate the number of days between two dates?
Enter your start date and end date in our calculator. It instantly shows the exact difference in days, weeks, months, and years. Toggle "Business days" to exclude weekends from the count.
How do I calculate a date 90 days from now?
Use the "Add Days" mode. Select today's date as the start, enter 90, and click calculate. The result shows the exact future date. You can also subtract days to find a past date.
How do I count business days excluding weekends?
Enable the "Business days only" option in our calculator. It automatically excludes Saturdays and Sundays from the count. You can also exclude US federal holidays for even more accurate business day calculations.
What happens when I add a month to 31 January?
You get 28 February, or 29 in a leap year. There is no universally correct answer, so the calculator clamps to the last valid day of the target month, which is what billing systems and most contracts do. Adding 30 days instead gives 2 March, and the difference matters when a deadline is defined one way and calculated the other.
Does the business-day count include public holidays?
No. It excludes Saturdays and Sundays only, because public holidays differ by country and often by region within one. For a contractual deadline expressed in working days, take the result and subtract the holidays that fall inside the range using a local calendar.