List all iOS timezones

TimeZoneManager.swift

class TimeZoneManager {    
    static let shared = TimeZoneManager()
    private init() {}

    private var continents = [String]()
    private var timeZonesList = [String: [String]]()
    
    var timeZones: [String: [String]] {
        get {
            for timeZone in TimeZone.knownTimeZoneIdentifiers {
                let continent = timeZone.components(separatedBy: "/")[0]
                if !continents.contains(continent) {
                    continents.append(continent)
                }
                var timeZonesInContinent = timeZonesList[continent] ?? [String]()
                if let zone = timeZone.components(separatedBy: "/").last {
                    if !timeZonesInContinent.contains(zone) {
                        timeZonesInContinent.append(zone)
                    }
                }
                timeZonesList[continent] = timeZonesInContinent
            }
            return timeZonesList
        }
    }
}