How to get Monday's date of the current week in swift

Question

I\'m trying to get Monday\'s date of the current week. This is treated as the first day of the week in my table view. I also need to get Sunday\'s of the current week. This

Answer 1

You can use calendar ISO8601 where the first weekday is Monday:

Swift 5.2 or later

extension Calendar {
    static let iso8601 = Calendar(identifier: .iso8601)
    static let iso8601UTC: Calendar = {
        var calendar = Calendar(identifier: .iso8601)
        calendar.timeZone = TimeZone(identifier: "UTC")!
        return calendar
    }()
}

---

let monday =
    Calendar.iso8601.dateComponents([.calendar, .yearForWeekOfYear, .weekOfYear], from: Date()).date!  // "Nov 9, 2020 at 12:00 AM"
print(monday.description(with: .current))   // "Monday, November 9, 2020 at 12:00:00 AM Brasilia Standard Time\n"
let mondayUTC =
    Calendar.iso8601UTC.dateComponents([.calendar, .yearForWeekOfYear, .weekOfYear], from: Date()).date!  // "Nov 8, 2020 at 9:00 PM" TimeZone -03:00
print(mondayUTC)   // "2020-11-09 00:00:00 +0000\n"

---

Implemented as a Date computer property extension:

extension Date {
    var mondayOfTheSameWeek: Date {
        Calendar.iso8601.dateComponents([.calendar, .yearForWeekOfYear, .weekOfYear], from: self).date!
    }
    var mondayOfTheSameWeekAtUTC: Date {
        Calendar.iso8601UTC.dateComponents([.calendar, .yearForWeekOfYear, .weekOfYear], from: self).date!
    }
}

---

let mondayOfTheSameWeek = Date().mondayOfTheSameWeek   // "Nov 9, 2020 at 12:00 AM"
print(mondayOfTheSameWeek.description(with: .current)) // "Monday, November 9, 2020 at 12:00:00 AM Brasilia Standard Time\n"
let mondayOfTheSameWeekAtUTC = Date().mondayOfTheSameWeekAtUTC  // "Nov 8, 2020 at 9:00 PM"
print(mondayOfTheSameWeekAtUTC) // "2020-11-09 00:00:00 +0000\n"