What counts as a day here
Each counted day is identified by the date it starts on. From Monday March 4 to Friday March 8 the days that pass start on the 4th, 5th, 6th and 7th, so the count is 4. The end date is not counted because that day has not passed yet. From a date to itself the answer is 0. Switch on the end date option and the 8th counts too, giving 5.
This is the same number a spreadsheet gives when you subtract one date from the other, and the number most programming languages give for the difference of two dates.
Days until and days since
For a countdown, put today in the start box and the event in the end box. For days since, put the earlier date in the start box and press Today on the end box. The answer is for the day you look at it, so it changes tomorrow.
If you copy a link, it holds the two dates you entered. When one of them came from Today, the link holds that day's date, not the word today, so anyone who opens it later sees the same count.
Turning a day count into weeks, months and years
A week is 7 days, so 100 days is 14 weeks and 2 days, and 365 days is 52 weeks and 1 day. Months and years are not fixed lengths, so there is no single way to divide days into them. A year is 365 days, or 366 across a leap day. Months run from 28 to 31 days: March 1 to April 1 is 31 days, and April 1 to May 1 is 30.
The line under the big number gives the exact years, months and days between the two dates, using whole months and the last day of the month when a month is too short. For the details, see the date difference calculator.
Common day counts
Notice periods, invoice terms, trial periods and warranty windows are often written as 14, 30, 60 or 90 days. Check whether the wording says calendar days, which is what this page counts, or business days, which skip weekends and holidays. For business days use the working days calculator. To find the date at the end of such a period, use the add and subtract calculator.