Weekday & Week Number
Enter any date to learn which day of the week it falls on, its ISO 8601 week number, day of the year, quarter, leap-year status and how far it is from today.
A mental shortcut
To find the weekday of a date in your head, memorise one anchor day per year and count forward in sevens; the "Doomsday" method popularised by John Conway uses the fact that 4/4, 6/6, 8/8, 10/10 and 12/12 all fall on the same weekday in any given year.