NSCalendar, why does setting the firstWeekday doesn't effect calculation outcome?

Question

i need to calculate the weekday for a given date, however, depending on the calendar a week can star on Monday and somwhere on Sunday

so i wanted to set it, to start

Answer 1

A useful function to get corrected weekday number for different firstWeekday cases

Swift 3.0

func dayOfWeek(day: Int, month: Int, year: Int) -> Int {
    let calendar = Calendar.current
    let dateComponents = DateComponents(year: year, month: month, day: day)

    guard let date = calendar.date(from: dateComponents) else {
        fatalError("Can't create date form specified date components")
    }

    var weekday = calendar.component(.weekday, from: date)

    //handling the case when calendar starts from Monday: firstWeekday == 2
    if calendar.firstWeekday == 2 {
        weekday = (weekday == 1) ? 7 : (weekday - 1)
    }

    return weekday
}