Creating a date with DateComponents - swift

Question

I want to get the first day and the last day of the week. But my results do not match the documentation from apple:
https://developer.apple.com/documentation/foundation/nsdatecomponents/1410442-weekday
This is my function:
func startAndEndDateOfWeek(weekOfYearWithYear: (week: Int,year: Int)) -> (start: Date, end: Date) {
var output = (start: Date.init(), end: Date.init())
let calendar = Calendar(identifier: .gregorian)
var firstDayComponents = DateComponents()
firstDayComponents.weekOfYear = weekOfYearWithYear.week
firstDayComponents.yearForWeekOfYear = weekOfYearWithYear.year
firstDayComponents.weekday = 1
let firstDay = calendar.date(from: firstDayComponents)
var lastDayComponents = DateComponents()
lastDayComponents.weekOfYear = weekOfYearWithYear.week
lastDayComponents.yearForWeekOfYear = weekOfYearWithYear.year
lastDayComponents.weekday = 2
let lastDay = calendar.date(from: lastDayComponents)
output = (start: firstDay!, end: lastDay!)
return output
}
.weekday = 2 -> leads to the sunday and not 0.
I also want to have the entire day and not 16:00.

Answer 1

A couple of observations:
In the Gregorian calendar, weekday = 1 means Sunday; weekday = 2 means Monday; etc. You can look at calendar.maximumRange(of: .weekday) to get the range of valid values, and you can look at calendar.weekdaySymbols to see what these weekDay values mean (e.g. “Sun”, “Mon”, “Tue”, “Wed”, “Thu”, “Fri”, and “Sat”).
You said:
I also want to have the entire day and not 16:00.
A Date object references a moment in time. So it can’t represent an “entire day”. But it can represent midnight (and midnight in your time zone is likely 4pm in GMT/UTC/Zulu).
You can, alternatively, return a DateInterval, which does represent a range of time.
func interval(ofWeek week: Int, in year: Int) -> DateInterval {
let calendar = Calendar.current
let date = DateComponents(calendar: calendar, weekOfYear: week, yearForWeekOfYear: year).date!
return calendar.dateInterval(of: .weekOfYear, for: date)!
}
And then
let formatter = DateIntervalFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .short
let year = Calendar.current.component(.year, from: Date())
let dateInterval = interval(ofWeek: 2, in: year)
print(formatter.string(from: dateInterval))
In a US locale, the interval starts on January 6th:
1/6/19, 12:00 AM – 1/13/19, 12:00 AM
Whereas in a German locale, the interval starts on the 7th:
07.01.19, 00:00 – 14.01.19, 00:00
If you want the start of the first day of the week and the last day of the week, you can do:
func startAndEndDate(ofWeek week: Int, in year: Int) -> (Date, Date) {
let date = DateComponents(calendar: calendar, weekOfYear: week, yearForWeekOfYear: year).date!
let lastDate = calendar.date(byAdding: .day, value: 6, to: date)!
return (date, lastDate)
}
And then
let formatter = DateFormatter()
formatter.dateStyle = .short
let year = Calendar.current.component(.year, from: Date())
let (start, end) = startAndEndDate(ofWeek: 2, in: year)
print(formatter.string(from: start), "-", formatter.string(from: end))