Date Calculator
Add or subtract days, weeks, months, years or business days from a date to find the resulting date.
Adding days to a date
Adding calendar days is straightforward: count forward that many days, rolling over into the next month and year as needed. Adding business days skips Saturdays and Sundays, so 10 business days from a Monday lands on the Friday of the following week.
Adding months
Months have different lengths, so "one month after" a date keeps the same day number where possible. When that day does not exist, the calculator uses the last day of the month. One month after January 31 is February 28 (or 29 in a leap year), not March 3.
90 days after January 15, 2025 is April 15, 2025. Three months after the same date is also April 15, but 90 days after November 15 is February 13, because November to February is 92 days.
When you need this
- Deadlines: "within 30 days of receipt" or "14 business days".
- Warranties and returns: a 90-day return window or a 2-year warranty.
- Visas and travel: passports often need to be valid 6 months beyond your stay.
- Medical and pregnancy timelines counted in weeks.
- Subscriptions and billing cycles that renew monthly or yearly.
To count the gap between two dates instead, use the days between dates calculator.
Frequently asked questions
What is 90 days from today?
Choose today as the start date, enter 90 and select calendar days. The calculator shows the exact date and day of the week.
How are business days calculated?
Business days skip Saturdays and Sundays. Public holidays are not skipped, so add extra days for any holidays in the period.
What happens when I add a month to January 31?
The result is the last day of February, because February 31 does not exist.
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.