Date Calculator: Add or Subtract Days
90 days after 20 October 2026 is Monday, 18 January 2027. The calculator opens on today’s date; change the date or the number of days.
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How it works
Pick a start date, enter how many days to add, and read the date. The page opens on today’s date in your time zone. A negative number goes back in time.
With “working days only” the calculator skips Saturdays and Sundays while counting. Starting on a weekend, the first working day after it is day 1.
Formula and worked example
Result date = start date + days, following the calendar, so month ends and leap days are handled for you.
Starting on 20 October 2026:
- 90 days later: Monday, 18 January 2027
- 90 days earlier: Wednesday, 22 July 2026
- 10 working days later: Tuesday, 3 November 2026
Frequently asked questions
How do I find the date 30, 60 or 90 days from today?
Leave the start date on today, type the number of days, and read the date. The result includes the weekday.
How do I go back in time?
Enter a negative number, for example −30 for the date 30 days ago.
Is the start date counted?
No. The start date is day 0, so one day after 1 January is 2 January.
What does "working days only" do?
It counts Monday to Friday and skips Saturdays and Sundays. Public holidays are not skipped; use the working days calculator when they matter.
How do leap years affect the result?
The calculator follows the Gregorian calendar, so 29 February exists in 2028 and not in 2027 or 2100. Adding 365 days to 1 January 2028 gives 31 December 2028.
How far can I go?
Up to 36,500 days (about 100 years) either way, from a start date between 1900 and 2100.
Sources and methodology
- RFC 3339 — Gregorian calendar and leap-year rules (accessed 2026-10-20)
Last updated 2026-10-20. Calculator version 1.0.0.Read how we calculate for our verification process.
Results are estimates for information only and are not financial, tax or legal advice.