🗓️ Date Calculator
Add or subtract any number of years, months, weeks and days from a date to find the exact calendar date it lands on.
Quick answer: Add the days to the start date on the calendar. For example, January 1, 2026 plus 90 days is Wednesday, April 1, 2026 (30 days left in January, 28 in February and 31 in March take you to March 31, then one more day).
Updated · Free · No sign-up · Works on any device
Date Calculator inputs
Result
Sunday, October 11, 2026 + 90 days
Saturday, January 9, 2027
| Start date | Sunday, October 11, 2026 |
| Added | 90 days |
| Result | Saturday, January 9, 2027 |
- Calendar days apart
- 90
- ISO week
- 1 of 2027
- Day of week
- Saturday
How the date calculator works
Dates are turned into a running day number, so adding days is a simple addition that automatically crosses month and year boundaries and includes February 29 in leap years. Months and years are applied on the calendar instead, keeping the same day of the month where possible.
Result = (Start + years × 12 + months, clamped to month end) ± (weeks × 7 + days)
Worked example
January 1, 2026 + 90 days: January has 30 days left after the 1st, February 2026 has 28 (2026 is not a leap year) and March has 31. That is 89 days to reach March 31, so the 90th day is Wednesday, April 1, 2026.
Subtracting: March 31, 2026 − 1 month gives February 28, 2026, because February has no 31st.
Because months are applied before days, "1 month and 1 day" from January 30 gives February 28 plus one day – March 1 in 2026.
Common offsets
| Offset | From Jan 1, 2026 |
|---|---|
| +30 days | Saturday, January 31, 2026 |
| +60 days | Monday, March 2, 2026 |
| +90 days | Wednesday, April 1, 2026 |
| +6 months | Wednesday, July 1, 2026 |
| +1 year | Friday, January 1, 2027 |
Tips
- Notice periods and deadlines: check whether the period is in calendar days or business days – use the business days calculator for the latter.
- Pregnancy, visas and warranties often use days or weeks rather than months; enter them in the matching box for an exact answer.
- Counting backwards: choose Subtract to find the date a period started, such as 180 days before a travel date.
Frequently asked questions
What happens when I add a month to January 31?
There is no February 31, so the result is clamped to the last day of the month: January 31 + 1 month is February 28, or February 29 in a leap year. Days are then added on top of that.
In what order are years, months, weeks and days applied?
Years and months are applied first (as whole calendar months), then weeks and days are added as a count of days. This matches how most people and contracts read "1 month and 10 days".
How do I find the date 90 days from today?
Leave the start date empty so it uses today, choose Add, enter 90 in Days and calculate. The result shows the date and the day of the week.
Is 3 months the same as 90 days?
Not quite. Three calendar months can be 89 to 92 days depending on which months and whether February has 29 days. Use the Months box for "3 months" and the Days box for "90 days".