Calendar.playground

import UIKit
import Foundation
import XCTest

private let formatter: Foundation.DateFormatter = {
    let dateFormatter = DateFormatter()
    dateFormatter.locale = Locale(identifier: "en_US_POSIX")
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ"
    return dateFormatter
}()

var calendar = Calendar.current
calendar.locale = Locale(identifier: "fi_FI")
calendar.firstWeekday = 2
print(calendar)

let dateInWeek16 = formatter.date(from: "2020-04-17 17:20:00 +0300")!
var components = calendar.dateComponents([.yearForWeekOfYear, .weekOfYear], from: dateInWeek16)

// weekday: 2 weekOfYear: 16 yearForWeekOfYear: 2020 isLeapMonth: false
print(components)

let firstDayInWeek = calendar.date(from: components)!
let day = calendar.component(.day, from: firstDayInWeek)


print("Day: \(day)")
XCTAssertEqual(day, 13, "Day did not match expected")

print("Date: \(firstDayInWeek)")
let expectedDate = formatter.date(from: "2020-04-13 00:00:00 +0300")!

// The problem here was that I was ignoring the timezone info
// With the timezone info in place, this works as expected
print(firstDayInWeek.timeIntervalSince1970)
print(expectedDate.timeIntervalSince1970)

print("Expt: \(expectedDate)")
XCTAssertEqual(firstDayInWeek, expectedDate, "Date did not match expected")

print(primerDíaDeLaSemana.IntervaloDeTiempoDesde1970)