Days between dates, add or subtract days, a D-day countdown and a day-of-the-week finder in one place.
Ages in years, months and days are on the Age Calculator.
Counted from today (, your device's date).
Works for any date from year 1 to 9999 (proleptic Gregorian calendar).
Days between dates counts calendar days from the start date to the end date. By default the start date is day 0, so Monday to Friday is 4 days; tick “Include the end date” to count both days (5). Business days are Monday–Friday and do not exclude public holidays, which vary by country.
Add / subtract moves a date by days, weeks, months, years or business days. When you add months and the target month is shorter (for example 31 January + 1 month), the result is the last day of that month (28 or 29 February).
Countdown shows how many days are left until an event, the way a “D-day” counter does (D-30 means 30 days to go). Day of the week tells you the weekday, ISO week number and day of the year for any date.