Date Calculator
Two tools in one. Project deadlines forward or backward by adding or subtracting years, months, weeks, and days from any start date. Or measure the exact span between two dates — including how many of those days are business days, handy for contracts, shipping estimates, and HR timelines.
How the Date Calculator works
The calculation follows the standard method used across the US — no shortcuts, no hidden assumptions. Here is exactly what happens behind the scenes:
- Adding months clamps to the end of short months (Jan 31 + 1 month = Feb 28/29).
- The difference mode counts calendar days inclusive of the start, exclusive of the end.
- Business days skip Saturdays and Sundays.
Frequently Asked Questions
How do I add 90 days to today’s date?
Set today as the start date, leave years/months/weeks at zero, enter 90 in the days field, and choose “Add”. The result includes the weekday so you can spot weekend landings immediately.
What counts as a business day here?
Monday through Friday. US federal holidays such as Thanksgiving or July 4th are not deducted automatically — subtract them manually if your deadline treats them as non-working days.
Does “add one month” mean 30 days?
No. Calendar-month addition preserves the day-of-month wherever possible: March 15 plus one month is April 15. Only month-end overflow gets clamped, e.g., January 31 becomes February 28 or 29.
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