Date Calculator
Add or subtract days, weeks, months, and years from any date to find the resulting date and day of the week.
Adds or subtracts a span from any date. Months and years adjust for varying month lengths and leap years.
How to use this calculator
Choose a start date, select Add or Subtract, and enter any combination of years, months, weeks, and days. The result date updates instantly. To count the gap between two dates instead, use our days between dates calculator.
How date math works
The calculator shifts the calendar by the amounts you enter, applying years and months first, then weeks and days. Because it uses real calendar dates, it correctly handles month lengths and leap years.
Worked example
Adding 90 days to a start date lands exactly three months later in day count — useful for return windows, probation periods, or project milestones.
Frequently asked questions
How do I add days to a date?
Pick a start date, choose 'Add,' and enter the number of days (or weeks, months, years). The calculator returns the resulting date and day of the week.
How do I subtract time from a date?
Choose 'Subtract' and enter the span. For example, subtracting 90 days from today gives the date three months ago, adjusted for actual month lengths.
How are months and years handled?
Adding months or years shifts the calendar accordingly and accounts for different month lengths and leap years, so adding one month to January 31 lands at the end of February.
What can I use this for?
Project deadlines, contract or notice periods, warranty and return windows, due dates, and any 'what date is X from now' question.