timezonecheck

//: Playground - noun: a place where people can play

import UIKit

let formatter = DateFormatter()

formatter.dateFormat = "yyyy MM dd"

let date = formatter.date(from: "2017 03 31")

if let url = URL(string: "https://raw.githubusercontent.com/dmfilipenko/timezones.json/master/timezones.json") {
    do {
        let contents = try String(contentsOf: url)
        let json = try JSONSerialization.jsonObject(with: contents.data(using: .utf8)!, options: .init(rawValue: 0))
         if let timeZones = json as? [[String: Any]] {
            for timeZone in timeZones {
                if let utcArr = timeZone["utc"] as? [String] {
                    for utc in utcArr {
                        formatter.timeZone = TimeZone(identifier: utc)!
                        //print(utc)
                        for i in 1...31 {
                            if formatter.date(from: "2017 03 \(i)") == nil {
                                print("problematic time zone = \(utc) on march \(i)")
                                formatter.timeZone = TimeZone(identifier: "UTC")!
                                if let date = formatter.date(from: "2017 03 \(i)") {
                                    print("same date with UTC = \(date)")
                                }
                            }
                        }
                        
                    }
                }
            }
        }
    } catch {
        // contents could not be loaded
    }
} else {
    // the URL was bad!
}