Gets a weekday name string.
DateTime.dayName(weekday [, numchar])
|weekday||An integer in the range 0 - 6 referring to a day of the week; 0 = Sunday.|
|numchar||An optional integer giving the maximum number of characters to return in the string.|
A string with the English name for the day of the week. If numchar is given, the string will be no more than numchar characters, allowing you to easily retrieve the name as an abbreviation.
|DateTime.dayName(2)||// returns "Tuesday"|
|DateTime.dayName(6,3)||// returns "Sat"|