Counting Days: Is Today Day 0 or Day 1?

Day 0 or day 1

Most date calculators count the days after the start date: the start date is day 0, tomorrow is day 1. Some rules say "including today" or "the first day counts", and then the last day comes one day sooner. Worked from Friday 13 November 2026:

The days from today calculator uses day 0. For a rule that includes today, type one day fewer.

Calendar days or working days

"30 days" almost always means calendar days: every day counts, weekends and holidays too. "30 working days" or "business days" counts Monday to Friday only and skips public holidays, which differ by country. In any run of 30 calendar days there are 20 to 22 weekdays, depending on the weekday you start on; in 90 days, 64 or 65. The 90 days from today page shows the exact weekday count for today, before holidays (UK dates are on the bank holidays page).

"Within 30 days" and deadlines

"Within 30 days" usually means on or before the 30th day after the start, so a refund requested on 13 November 2026 is in time up to and including Sunday 13 December 2026. When the last day falls on a weekend, some rules move it to the next working day and some do not: the wording of your contract or the law that applies decides, not the calendar. When it matters, check the exact wording.

Months are not 30 days

Adding a month keeps the day of the month (13 November → 13 December), which is 28 to 31 days later. "30 days" and "1 month" agree only after a 30-day month: from 1 January 2027, 30 days is Sunday 31 January while 1 month is Monday 1 February. Over 6 months the gap grows: 180 days from 1 January 2027 is 30 June, 6 months is 1 July.

Time zones, clock changes and leap years

A date count runs on the calendar where you are, so close to midnight the answer can differ between two countries. Clock changes do not move a date count, because days are counted, not hours; they only matter when you count hours. Leap years add 29 February: 365 days from 1 March 2027 is 29 February 2028, not 1 March.