Calculate Days
Add days or weeks to a date, count days between two dates, or look up an ISO week number—optionally skipping weekends and public holidays by country.
Add days to a date
Add weeks to a date
Count days between two dates
Find the week number for a date
How these day calculators work
These tools work on calendar dates (year-month-day), not on a city’s wall clock. Pick a date in the form, choose how days should be counted, and the server returns a result for that rule set. That is different from converting a meeting hour across time zones—for live city clocks and overlap windows, use the World Meeting Planner or a time zone converter.
Add days starts from your chosen date and moves forward until it has counted the number you entered. With All days, that is a straight calendar shift (for example, 1 March plus 10 days lands on 11 March). With Exclude weekends, only Monday–Friday count toward that total, so the final date can land further out. With holiday options turned on, any date stored as a public holiday for the selected country is also skipped; when holidays were hit, the result line lists those dates.
Count days measures the span between a beginning and an end date under the same four counting modes. The checkbox Include end date in calculation decides whether the end date itself is in the count (default is on). Example with all days: from 1 March to 5 March is 4 days with the box off, and 5 with it on. Add weeks always adds whole calendar weeks (7-day blocks) and never applies weekend or holiday filters. The week number tool reports ISO-8601 week data for the date you pick.
Typical uses: a delivery promise of “10 business days,” how many calendar or working days sit between two deadlines, or which ISO week a ship date falls in. Holiday filtering uses this site’s public-holiday list for the country you select. For more context on business days across borders, see business days, holidays, and time zones. Results are general reference—not legal, payroll, or airline advice.
Calculate Days FAQ
What can I do on this page?
Four calculators on one page: add days to a date, add weeks to a date, count days between two dates, and look up a date’s ISO week number (plus how many weeks that ISO year has and how many weeks remain after the current week).
How do I add days to a date?
Choose a start date and a positive whole number of days to add. Then pick a counting mode: all calendar days, exclude weekends, exclude public holidays, or exclude weekends and holidays. If either holiday mode is selected, also pick a country so the tool can look up that country’s holiday dates. Click Calculate for the resulting date.
The count moves forward from the start date. It does not treat the start date itself as “day 1” of the add.
Enter only positive integers (for example 10); the form rejects empty or non-numeric values.
How do I count days between two dates?
Enter a beginning date and an end date, then choose the same weekend/holiday options as Add Days. Turn Include end date in calculation on if the end date should count (the UI defaults to on; the result label notes when one day was added for that option). A country is used whenever public holidays are excluded.
For weekend and holiday modes, if the end date is before the beginning date, the tool swaps them so the span is still counted forward. Same-day ranges with the include box off return zero days; with the box on, they return one day.
What does “Include end date” change?
With the box off, counting treats the end date as exclusive: from 1 March to 5 March is 4 calendar days. With the box on, the end date is included: the same pair is 5 calendar days. The same include rule applies when you exclude weekends or holidays—only the set of days that qualify changes, not what “include end” means.
What does “Exclude weekends / public holidays” mean?
All days counts every calendar day. Exclude weekends skips Saturdays and Sundays only (Friday and Monday still count; there is no separate Middle East weekend mode). Exclude public holidays skips dates present in this site’s public-holiday table for the country you selected. Exclude weekends and public holidays skips both.
When holidays are skipped, the result text may list the holiday dates that were hit. Holiday coverage depends on what is stored for that country and year; regional or employer-specific days may be missing. Treat the list as a planning aid, not an official government calendar.
How does Add Weeks work?
Pick a date and a positive whole number of weeks, then calculate. The tool adds that many calendar weeks (each week is seven days) with no weekend or holiday filter. Those filters exist only on Add Days and Count Days, because “add two weeks” here means a fixed 14-day calendar shift, not “ten business days.” For business-day style math, use Add Days with weekends (and optionally holidays) excluded.
What does the week number calculator show?
For the date you pick, it returns the ISO-8601 week number, how many weeks that ISO week-numbering year has (52 or 53), and how many weeks remain after the current week number (total − current). ISO weeks start on Monday. Week 1 is the week that contains the year’s first Thursday. Early January or late December dates can belong to the neighboring ISO year—the result labels show which ISO year was used.
That is not the same as every U.S. school or payroll “week of the year” scheme (some start on Sunday or number weeks differently). If your process requires a company-specific week map, confirm against that map rather than ISO alone.
What should I not expect this page to do?
It does not convert clock times across time zones, subtract days, or accept fractional days. Weekends are Saturday and Sunday only. Holiday skips follow this site’s country holiday lists—not every local observance worldwide. Always double-check high-stakes deadlines with your contract, HR calendar, or airline rules.