Date Calculator
Add or subtract years, months, weeks and days to any date in one step.
The Date Calculator does date arithmetic the way people actually phrase it: 'What date is 90 days from today?', 'What day will it be 6 weeks after March 1?', or 'When was 1 year and 3 months before my lease started?' Enter any start date, choose add or subtract, and set the years, months, weeks and days — the result appears instantly with its weekday.
The tool follows real calendar rules rather than rough averages. Adding a month to January 31 does not give February 31 (which does not exist); it clamps to February 28 or 29, the way calendars actually work. Leap years are handled automatically, so adding one year to February 29, 2028 lands correctly on February 28, 2029.
Common uses: counting ahead to deadlines and court dates, planning project timelines, calculating warranty or subscription end dates, scheduling medication refills, or checking when a notice period finishes. All arithmetic runs locally in your browser.
Result (add 1y 0m 0w 0d)
Friday, January 1, 2027
365 days after the start date
How to use the Date Calculator
- Pick the start date.
- Choose Add or Subtract.
- Enter the number of years, months, weeks and/or days (leave unused fields at 0).
- Read the resulting date with its weekday.
- The tool clamps impossible dates like Feb 30 automatically — no surprises.
Frequently asked questions
How do I calculate a date 90 days from today?
Set the start date to today, choose Add, enter 90 in the Days field, and read the result. The tool adds 90 calendar days, skipping no days — weekends and holidays count unless you use the Business Days Calculator instead.
What happens when adding a month to the 30th or 31st?
The result clamps to the last valid day of the target month. January 31 plus 1 month gives February 28 (or 29 in a leap year), not March 2 or 3. This matches how leases, payroll and most legal deadlines interpret 'a month later'.
Does the calculator handle leap years?
Yes. Adding a year to a date near the end of February in a leap year lands on the correct February date of the next year, and day counts across February 29 are always accurate because every calculation uses real calendar dates.
Is 'a month' always 30 or 31 days?
No — and this tool never assumes. Calendar months have 28 to 31 days. When you add months, it adds actual calendar months; when you add weeks or days, it adds exact 7-day or 1-day steps. Mixing months and days applies months first, then days.
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