Add or Subtract Days Calculator
Add or subtract days, weeks, months or years from any date.
About the Add or Subtract Days Calculator
Need to know the date 90 days from now, or 45 days before a deadline? The AlarmDaddy Add or Subtract Days Calculator shifts any date forward or backward by a number of days, weeks, months, or years and returns the resulting date along with the day of the week.
Enter a starting date, choose to add or subtract, and enter the amount and unit. The calculator returns the new date and which weekday it falls on. It is perfect for notice periods, payment due dates, return-policy windows, warranty expiry, gestation periods, and legal or compliance deadlines that are defined as "X days from" an event.
How to use this calculator
- 1Enter the starting date.
- 2Choose add or subtract.
- 3Enter the amount and pick the unit (days, weeks, months, years).
- 4Read the resulting date and its day of the week.
The formula
The calculator advances or rewinds the calendar by the requested interval, rolling over month and year boundaries correctly and handling leap years. Month arithmetic clamps to the last valid day (e.g. adding one month to Jan 31 yields Feb 28/29).