Date.DayOfWeek - Default for argument firstDayOfWeek ???
According to the documentation the default for the argument firstDayOfWeek should be Day.Sunday!
October 31st, 2010 was a Sunday but Date.DayOfWeek(#date(2010,10,31)) returns 6.
Has this argument somehow been localized? Here in Germany the week starts on Monday, thus 6 would correctly represent a Sunday for Day.Monday.
Date.DayOfWeek(dateTime as any, optional firstDayOfWeek as nullable number) as nullable number
Returns a number between 0 and 6 representing the day of the week in the provided datetime value dateTime. This function takes an optional Day value, firstDayOfWeek, to set the first day of the week for this relative calculation. The default value firstDay is Day.Sunday. Valid values are: Day.Sunday, Day.Monday, Day.Tuesday, Day.Wednesday, Day.Thursday, Day.Friday, and Day.Saturday.
dateTime: A date, datetime, or datetimezone value from which the day of the week is determined.
firstDayOfWeek: A Day type representing the first day of the week for this calculation.