Date Calculator: Add or Subtract Days
Choose a start date, pick whether to add or subtract, and enter a number of days to find the exact resulting date — with the day of the week.
Working forward or backward from a date
Adding days to a date sounds simple, but month lengths and leap years make mental maths error-prone. This calculator advances or rewinds the calendar one day at a time internally, so crossing month and year boundaries is always handled correctly.
The result includes the weekday, which is often the detail you actually need — for example, knowing that a 90-day deadline lands on a weekend.
Everyday examples
Find the due date 30, 60 or 90 days after an invoice; the end of a 14-day return window; a 21-day quarantine or notice period; or the date 100 days before an event you're planning.
Subtracting works the same way — useful for back-dating a start point from a known deadline.
Frequently asked questions
What date will it be in 90 days?
Set today as the start date, choose 'Add days', and enter 90. The calculator shows the exact date and weekday 90 days from now.
Does it count weekends?
Yes, this tool counts every calendar day including weekends. To count only working days, use the Working Days Calculator instead.