Date calculator
Add or subtract years, months, weeks, days, hours and minutes, or a number of business days. You get the date, its weekday, ISO week and day of the year.
Example: 90 days after 9 October 2026. Pick your own date and amounts above.
Result
after 2026-10-09- ISO week
- Week 1 of 2027
- ISO week date
- 2027-W01-4
- Day of the year
- 7 of 365
- Days left in the year
- 358
- Quarter
- Q1
- US week (Sunday start)
- 2
- Leap year
- No, 2027 has 365 days
How it works
Years and months are added on the calendar, then weeks and days. When the day doesn't exist in the new month, the date moves back to the month's last day: 31 January plus 1 month is 28 February (29 in a leap year). The page tells you when that happens, because adding the month back won't return you to the 31st.
Hours and minutes are real elapsed time. Across a daylight saving change, adding 24 hours can land at a different clock time than adding 1 day. Pick a time zone to see the difference.
Business days skip Saturdays, Sundays and any holidays you list. One business day after a Friday is the next Monday. Holidays differ by country and company, so none are built in.
To find the time between two dates, use the time difference calculator. For the week number of a date, use week number.