X is a temporal scalar/vector.
startFromSunday is a Boolean value indicating whether a week starts from Sunday. The default value is true. If startFromSunday=false, a week starts from Monday.
Return integer(s) to represent of the corresponding weekday(s) of X.
If startFromSunday=true, 0 means Sunday, 1 means Monday, …, and 6 means Saturday.
If startFromSunday=false, 0 means Monday, 1 means Tuesday, …, and 6 means Sunday.
$ weekday 2012.12.05; 3 $ weekday(2012.12.05, false); 2 $ weekday 2013.05.23T12:00:00; 4 $ weekday(2014.01.11T23:04:28.113); 6 $ weekday 2012.12.05 2012.12.06 2013.01.05; [3,4,6]