Add or Subtract Time From Any Date
This date calculator answers "what date will it be in x days" (or weeks, months, or years, in either direction) by adding or subtracting a chosen amount from a base date, then telling you both the resulting calendar date and its weekday. Add days to date or subtract days from date, calculate future date or calculate past date, same tool either way, just flip Operation between add and subtract.
How to Use This Date Calculator
Enter a Base date (ISO format, e.g. 2026-01-01), choose Operation (add or subtract), set Amount, and pick Unit (days, weeks, months, or years). Click Generate, this date add subtract calculator returns the resulting date as an ISO date plus its full weekday name, e.g. "2026-02-28 (Saturday)". To use this as a days from today calculator, type today's actual date into Base date, since it isn't filled in automatically.
Why Month and Year Math Is Trickier Than It Looks
Naive date math breaks on month-end dates: adding 1 month to January 31st has no real "February 31st" to land on. This date calculator handles it the way a calendar app does, clamping to the target month's actual last valid day, so add months to date from January 31 plus 1 month correctly gives February 28th (or the 29th in a leap year), not an overflow into March. The same clamping applies going backward and to year math (a February 29th leap day plus 1 year correctly lands on February 28th of the following, non-leap year), so the direction and size of the result always make sense relative to the base date.
What This Calculator Doesn't Do
Base date needs an explicit date value, this tool doesn't parse relative phrases like "today" or "next Friday", you type the actual date yourself. All math happens in UTC with no time-of-day component, dates are treated as whole calendar days, not specific moments, if you need to add or subtract hours and minutes across timezones, use a timestamp converter instead.