About adding or subtracting time from a date
Figuring out what date falls a certain number of days, weeks, months, or years from today (or from any other date) is a common everyday calculation — planning a due date, checking a return deadline, or working out an anniversary. This tool takes a base date plus a number and unit, and calculates the resulting date after adding or subtracting that amount.
How the resulting date is calculated
Day and week additions simply shift the date by that many calendar days. Month and year additions move the calendar month/year forward or backward by that amount while trying to keep the same day-of-month; if that day doesn't exist in the target month (like adding 1 month to January 31st, which has no February 31st), the tool automatically clamps the result to the last valid day of that month rather than producing an invalid date.
Frequently asked questions
- What happens when adding a month lands on a day that doesn't exist, like January 31 + 1 month?
- Since February doesn't have 31 days, the tool clamps the result to February's last valid day (the 28th, or 29th in a leap year) rather than erroring out or rolling over into March — this matches how most calendar and spreadsheet software handles the same situation.
- How does the tool show how many days ago or in the future the result is?
- Alongside the calculated date, it also shows how many days that date is from today, giving you an at-a-glance sense of whether it's coming up soon or still far off, in addition to the exact date and day of the week.
- Can I subtract time instead of adding it?
- Yes — choosing subtract with the same number and unit inputs calculates the date that many days, weeks, months, or years before your base date, using the same logic (including the same end-of-month clamping) as addition.