Add or Subtract Days Calculator
Add days to a date or subtract days to find dates such as 30 or 100 days from a chosen starting date.
How to use Add or Subtract Days Calculator
Add a positive or negative number of days to a base date. Use it to find dates such as 100 days later or two weeks earlier.
Displayed values follow the definitions stated above.
Find a date a chosen number of days before or after
Instead of stepping through calendar pages, enter a starting date and the number of days to move. This tool counts every calendar day, including weekends and holidays; use the business-days calculator for working-day deadlines.
Use a positive number for a later date and a negative number for an earlier date.
Recommended steps
- Enter the base date.
- Enter a positive number to move forward or a negative number to move backward.
- Check the result in the weekday or business-days calculator when those rules matter.
How to interpret the result
- Thirty days from a date is not always the same as one calendar month later.
- Crossing February 29 can produce a different result in a leap year.
- Legal and contractual deadlines may define separate start-day and business-day rules.
Frequently asked questions
Does a 100-day count include the starting date?
This calculator treats the base date as day zero and moves exactly 100 days. If an event calls the start day day one, add 99 days instead.
Is one month the same as 30 days?
Not always. Calendar months contain 28 to 31 days, while this tool moves an exact number of days.
Are weekends and holidays included?
Yes. Use the business-days calculator when weekends or selected holidays should be skipped.