Date Calculator — Add or Subtract Time
Add or subtract days, weeks, months, and years from any date. Skip weekends for business-day math and copy the result as a date or a Unix timestamp.
Frequently Asked Questions
›How do I add days to a date?
Pick a start date, type the number of days, and choose Add. The new date appears instantly, with the weekday, the ISO 8601 string, and the Unix timestamp.
›Can it skip weekends?
Yes. Turn on business days and the calculator counts only Monday to Friday, which is what you want for delivery dates, SLA windows, and notice periods.
›How are months handled at the end of a month?
Adding one month to January 31 gives February 28 (or 29 in a leap year). The day is clamped to the last day of the target month, which matches how date libraries and spreadsheets behave.
›Can I go backwards in time?
Yes. Choose Subtract to move backwards. This answers questions like '90 days before the deadline' or 'what date was 18 months ago'.