Question

How to find the dates of the last Sunday of each month of a given year in Swift

Answer 1

import Foundation

// Return all last Sundays of each month in a given year
struct LastSundaysOfYear: Sequence, IteratorProtocol {
    let year: Int
    private var month: Int

    init(year: Int) {
        self.year = year
        self.month = 1
    }

    mutating func next() -> Date? {
        guard month <= 12 else { return nil }

        let calendar = Calendar.current

        // Last day of the month
        let comps = DateComponents(year: year, month: month + 1, day: 0)
        var date = calendar.date(from: comps)!

        // Walk backward to Sunday
        while calendar.component(.weekday, from: date) != 1 { // Sunday = 1
            date = calendar.date(byAdding: .day, value: -1, to: date)!
        }

        month += 1
        return date
    }
}

// Main
let args = CommandLine.arguments
let year: Int =
    args.count > 1
        ? Int(args[1]) ?? 2026
        : 2026

let formatter = DateFormatter()
formatter.dateFormat = "MM/dd/yyyy"

for date in LastSundaysOfYear(year: year) {
    print(formatter.string(from: date))
}



/*
run:

01/25/2026
02/22/2026
03/29/2026
04/26/2026
05/31/2026
06/28/2026
07/26/2026
08/30/2026
09/27/2026
10/25/2026
11/29/2026
12/27/2026

*/

 

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