Add or subtract days, weeks, months or years from any starting date.
This tool takes any starting date and either adds or subtracts a chosen number of days, weeks, months or years from it, returning the exact resulting calendar date along with which weekday it falls on. It handles month-length differences and leap years automatically, so you never have to manually track how many days are in the month you're crossing into.
Adding 30 days to a date and adding 1 month to the same date usually give different results, since months range from 28 to 31 days long. This calculator handles the month and year units by shifting the actual calendar month and year forward or backward — so adding 1 month to January 31st correctly rolls over based on how many days the destination month actually has, rather than assuming a fixed 30-day month.
This is the exact calculation behind figuring out a deadline that's '90 days from signing', a warranty that expires '2 years from purchase', a return window that's '30 days from delivery', or a reminder that should fire '2 weeks before' an event. Legal contracts, subscription terms, and personal reminders all frequently specify a duration relative to a starting date rather than a fixed calendar date, and this tool converts that relative duration into the actual date you need to plan around.
The main result shows the calculated date in full, readable form, along with which day of the week it falls on — useful for spotting whether a deadline lands on a weekend — and the same date in ISO 8601 format (YYYY-MM-DD), which is handy for entering into spreadsheets, forms or code where a standardized date format is expected.
Days and weeks are exact units — 2 weeks is always exactly 14 days, regardless of which months it crosses — while months and years are calendar-based units that can span a different number of actual days depending on where you start. If your deadline is defined in a legal document as 'business days' rather than plain days, remember this tool counts every calendar day; use the Business Days Calculator instead if weekends need to be skipped.
The calculation rolls over to the correct date using standard date arithmetic — for example, adding 1 month to January 31st will resolve to whatever date JavaScript's date engine determines, typically the equivalent day in the following month, which may not be the 31st if that month is shorter.
Yes, select 'Subtract' as the operation and the calculator will move backward by the amount and unit you specify.
Yes, if the resulting date lands on February 29th of a year that isn't a leap year, the underlying date engine automatically resolves it to a valid nearby date.
Yes, there's no practical limit on the amount you can add or subtract.
YYYY-MM-DD, the international standard date format, which sorts correctly and is unambiguous across regions that otherwise write dates in different orders.