The counting rules we use, so you can trust the answer for deadlines, due dates and countdowns.
When you ask for "30 days from today", we start from today and count 30 days forward, so tomorrow is day 1. This is how deadlines, notice periods, return windows and shipping estimates are normally counted. "30 days ago" counts backward the same way.
Dates change at midnight, and midnight comes at different times around the world. Every page works out the answer on your own device, using your clock and time zone, so the date you see is right where you are. Pages are first drawn for US Eastern time, then updated instantly in your browser.
A week is exactly 7 days. Months and years follow the calendar: 1 month after March 15 is April 15. If the day does not exist in the target month, we use the last day of that month, so 1 month after January 31 is February 28 (or 29 in a leap year). This matches how banks, spreadsheets and most programming languages handle month arithmetic.
Business days are Monday to Friday. Public holidays differ by country, province, state and even employer, so every business-day answer shows two results: weekdays only, and weekdays without the public holidays where you are. We pick your country and region from your device settings, and you can change it at any time.
We cover 13 countries and 47 regions. Every list is compared, date by date, with the official list the government publishes, including substitute days when a holiday falls on a weekend. Holidays that are only announced shortly before the day (for example Eid in some countries, or one-off holidays for elections) are added once announced, and we re-check the official sources every month. See all lists on our public holidays pages.
We use ISO-8601 week numbers: weeks start on Monday, and week 1 is the week that contains the year's first Thursday. That is the international standard used in Europe and by most business software.
Fixed holidays use their calendar date. Moving holidays follow their official rules, for example US Thanksgiving is the fourth Thursday of November. Easter uses the standard Gregorian computus. Chinese New Year dates come from published lunar calendar tables.
Everything is calculated in your browser. Dates you type, including birthdays, are never sent to us.