Date calculator
The date calculator adds or subtracts years, months, weeks and days from a start date and shows the exact result with its weekday. Months are added first and clamped to the end of shorter months, then weeks and days are added, so adding one month to January 31 gives the last day of February.
Date after adding 250 days
Sunday, July 4, 2027
| Start date | Tuesday, October 27, 2026 |
|---|---|
| Difference | 250 days (35 weeks, 5 days) |
| Day of year | 185 of 365 |
| ISO week | Week 26 |
| ISO date | 2027-07-04 |
How to use it
- Pick a start date, or leave it as today.
- Choose add or subtract.
- Enter any mix of years, months, weeks and days.
- Read the resulting date, then use the day count to check it.
Questions
How does the calculator handle months of different lengths?
Adding months keeps the same day of the month when it exists, and otherwise uses the last day of the target month. Adding 1 month to January 31 gives February 28 (or 29 in a leap year).
Is the start day counted?
No. The start date is day 0, so adding 1 day to Monday gives Tuesday.
What is the largest range supported?
Years 1 through 9999 in the Gregorian calendar.
Last reviewed 2026-10-27. Calculations use the proleptic Gregorian calendar in UTC, so daylight saving time never shifts a result. Other calculators: Days between dates, Age calculator, Business days calculator.