Free date calculator to find a future or past date by adding or subtracting any combination of days, weeks, months, and years.
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Need to find a deadline 90 days from now? Or what date was 6 months ago? Our date calculator adds or subtracts any combination of days, weeks, months, and years from any starting date.
Date calculations are complex because months have different lengths, years can be leap years, and adding months doesn't always result in a valid date (like adding 1 month to January 31). Our calculator handles all these edge cases correctly. Month and leap-year handling follows the Gregorian calendar, and dates use the ISO 8601 standard — which is why adding a calendar month to January 31 lands on the last valid day of February rather than an invalid date.
Example
A NET-30 invoice dated March 3 is due April 2 — add 30 days to the invoice date to find the deadline.
Find a lease or contract end date: a 12-month lease starting June 1 ends May 31 the following year.
Count forward to plan ahead — for example, the date 8 weeks from today for a trip, party, or launch.
Track a 90-day prescription refill or a legal notice period by adding the interval to the start date.
Automatically handles months of different lengths and leap years.
Add or subtract in days, weeks, months, or years.
Perfect for calculating deadlines and timelines.
If the resulting month doesn't have that day, it uses the last day of the month. For example: January 31 + 1 month = February 28 (or 29 in a leap year).
When adding 'years', the calculator adds calendar years, not 365 days. Adding 1 year to March 1, 2024 gives March 1, 2025, regardless of whether there was a leap year.
Enter today's date, choose Add, and type 90 in the days field. The calculator instantly shows the resulting date and its day of the week. The same works for any number of days, weeks, months, or years — e.g. 90 days from March 3, 2024 is June 1, 2024.
Choose Subtract and enter the offset. For example, to find the date 30 days before a due date, set the due date as the start date, select Subtract, and enter 30 days — the result is your latest start-by date.
This calculator adds or subtracts calendar days, so weekends and public holidays are included in the count. For business-days-only math that skips weekends, use a working-days or days-between calculator with the weekday breakdown instead.