Swift 中具有正确时区的日期范围

Question

I know there is a lot of questions about time zones and dates but I really having hard time to figure this out.

My time zone is GMT+3 (That's what my physical device says)

I'm trying to get the range of the next week starting from Sunday. So it need to be Sep 27 ... Oct 3

Every night at 09:PM the results that I'm getting is from Sep 28 ... Oct 4. It's stays that way until 03:AM

The current time that I'm writing this question is 2:AM and it's shows me this range from Sep 28.

I made an extension for Date and added this variables (I'm using SwiftDate also).

var closedRange: ClosedRange<Date> {
        let d = Date() //.timeInterval - Fix the problem until 03:AM
        let calendar = Calendar.autoupdatingCurrent
        let min = calendar.date(byAdding: .day, value: 0, to: d.nextWeekday(.sunday))!
        let max = calendar.date(byAdding: .day, value: 6, to: d.nextWeekday(.sunday))!
        return min...max
    }

If I adding this var to d the date is correct. but after 3:AM it's messed up again.

var timeInterval: Date{
        var date = self
        date.addTimeInterval(TimeInterval(TimeZone.current.secondsFromGMT(for: self)))
        return date
    }

Later in view:

let range = Date().closedRange
    
DatePicker(LocalizedStringKey("Choose day:"), selection: $shift.date, in: range, displayedComponents: .date)

The problem also happens when I get the next week as String or Int. It starts from Sep 28 instead Sep 27 (again depends on my location time)

var nextWeek: [String]{
        
        let d = Date()
        var daysArr = [String]()
        let dateFormat = DateFormatter()
        let calendar = Calendar.autoupdatingCurrent
        let dayOfWeek = calendar.component(.weekday, from: d.nextWeekday(.sunday))
        let weekdays = calendar.range(of: .weekday, in: .weekOfYear, for: d.nextWeekday(.sunday))!
        let days = (weekdays.lowerBound ..< weekdays.upperBound).compactMap { calendar.date(byAdding: .day, value: $0 - dayOfWeek, to: d.nextWeekday(.sunday)) }
        
        dateFormat.dateFormat = DateFormats.format11.rawValue
        
        for d in days{
            daysArr.append(dateFormat.string(from: d))
        }
        
        return daysArr
        
    }

The same problem happens with this array of dates.

var nextWeekAsDates: [Date]{
        
        let d = Date()
        var daysArr = [Date]()
        let calendar = Calendar.autoupdatingCurrent
        let dayOfWeek = calendar.component(.weekday, from: d.nextWeekday(.sunday))
        let weekdays = calendar.range(of: .weekday, in: .weekOfYear, for: d.nextWeekday(.sunday))!
        let days = (weekdays.lowerBound ..< weekdays.upperBound).compactMap { calendar.date(byAdding: .day, value: $0 - dayOfWeek, to: d.nextWeekday(.sunday)) }
                
        for d in days{
            daysArr.append(d)
        }
        
        return daysArr
        
    }

Answer 1

You can simply get todays component weekOfYear advanced by 1, the yearForWeekOfYear and get the date from those components. That will be the start of the next week. If you need the end of it you can get the start of the following week which marks the end of it:

extension Calendar {
    static let gregorian: Calendar = .init(identifier: .gregorian)
}

---

extension Date {
    func nextWeekOfYear(using calendar: Calendar = .gregorian) -> Int {
        calendar.component(.weekOfYear, from: self) + 1
    }
    func yearForWeekOfYear(using calendar: Calendar = .gregorian) -> Int {
        calendar.component(.yearForWeekOfYear, from: self)
    }
    func startOfNextWeek(using calendar: Calendar = .gregorian) -> Date {
        DateComponents(calendar: calendar, weekOfYear: nextWeekOfYear(using: calendar), yearForWeekOfYear: yearForWeekOfYear(using: calendar)).date!
    }
}

---

Date().startOfNextWeek()  // "Sep 27, 2020 at 12:00 AM"

---

If you need a range:

var range: Range<Date> {
    let min = Date().startOfNextWeek()
    return min..<min.startOfNextWeek()
}

print(range) //  "2020-09-27 03:00:00 +0000..<2020-10-04 03:00:00 +0000\n"