¿Cómo obtener la zona horaria de un usuario?

¿Alguien conoce alguna forma de obtener la zona horaria de un usuario en Swift?

Obtengo una hora específica en la que algo está en la televisión de una base de datos y luego necesito restar / sumar desde donde están ubicados para mostrarles la hora correcta en que está encendido.

editar / actualizar:

Xcode 8 o posterior • Swift 3 o posterior

var secondsFromGMT: Int { return TimeZone.current.secondsFromGMT() }
secondsFromGMT  // -7200

si necesita la abreviatura:

var localTimeZoneAbbreviation: String { return TimeZone.current.abbreviation() ?? "" }
localTimeZoneAbbreviation   // "GMT-2"

si necesita el identificador de zona horaria:

var localTimeZoneIdentifier: String { return TimeZone.current.identifier }

localTimeZoneIdentifier // "America/Sao_Paulo"

Para conocer todas las abreviaturas de zonas horarias disponibles:

var timeZoneAbbreviations: [String:String] { return TimeZone.abbreviationDictionary }
timeZoneAbbreviations   // ["CEST": "Europe/Paris", "WEST": "Europe/Lisbon", "CDT": "America/Chicago", "EET": "Europe/Istanbul", "BRST": "America/Sao_Paulo", "EEST": "Europe/Istanbul", "CET": "Europe/Paris", "MSD": "Europe/Moscow", "MST": "America/Denver", "KST": "Asia/Seoul", "PET": "America/Lima", "NZDT": "Pacific/Auckland", "CLT": "America/Santiago", "HST": "Pacific/Honolulu", "MDT": "America/Denver", "NZST": "Pacific/Auckland", "COT": "America/Bogota", "CST": "America/Chicago", "SGT": "Asia/Singapore", "CAT": "Africa/Harare", "BRT": "America/Sao_Paulo", "WET": "Europe/Lisbon", "IST": "Asia/Calcutta", "HKT": "Asia/Hong_Kong", "GST": "Asia/Dubai", "EDT": "America/New_York", "WIT": "Asia/Jakarta", "UTC": "UTC", "JST": "Asia/Tokyo", "IRST": "Asia/Tehran", "PHT": "Asia/Manila", "AKDT": "America/Juneau", "BST": "Europe/London", "PST": "America/Los_Angeles", "ART": "America/Argentina/Buenos_Aires", "PDT": "America/Los_Angeles", "WAT": "Africa/Lagos", "EST": "America/New_York", "BDT": "Asia/Dhaka", "CLST": "America/Santiago", "AKST": "America/Juneau", "ADT": "America/Halifax", "AST": "America/Halifax", "PKT": "Asia/Karachi", "GMT": "GMT", "ICT": "Asia/Bangkok", "MSK": "Europe/Moscow", "EAT": "Africa/Addis_Ababa"]

Para conocer todos los nombres de zonas horarias (identificadores) disponibles:

var timeZoneIdentifiers: [String] { return TimeZone.knownTimeZoneIdentifiers }
timeZoneIdentifiers           // ["Africa/Abidjan", "Africa/Accra", "Africa/Addis_Ababa", "Africa/Algiers", "Africa/Asmara", "Africa/Bamako", "Africa/Bangui", "Africa/Banjul", "Africa/Bissau", "Africa/Blantyre", "Africa/Brazzaville", "Africa/Bujumbura", "Africa/Cairo", "Africa/Casablanca", "Africa/Ceuta", "Africa/Conakry", "Africa/Dakar", "Africa/Dar_es_Salaam", "Africa/Djibouti", "Africa/Douala", "Africa/El_Aaiun", "Africa/Freetown", "Africa/Gaborone", "Africa/Harare", "Africa/Johannesburg", "Africa/Juba", "Africa/Kampala", "Africa/Khartoum", "Africa/Kigali", "Africa/Kinshasa", "Africa/Lagos", "Africa/Libreville", "Africa/Lome", "Africa/Luanda", "Africa/Lubumbashi", "Africa/Lusaka", "Africa/Malabo", "Africa/Maputo", "Africa/Maseru", "Africa/Mbabane", "Africa/Mogadishu", "Africa/Monrovia", "Africa/Nairobi", "Africa/Ndjamena", "Africa/Niamey", "Africa/Nouakchott", "Africa/Ouagadougou", "Africa/Porto-Novo", "Africa/Sao_Tome", "Africa/Tripoli", "Africa/Tunis", "Africa/Windhoek", "America/Adak", "America/Anchorage", "America/Anguilla", "America/Antigua", "America/Araguaina", "America/Argentina/Buenos_Aires", "America/Argentina/Catamarca", "America/Argentina/Cordoba", "America/Argentina/Jujuy", "America/Argentina/La_Rioja", "America/Argentina/Mendoza", "America/Argentina/Rio_Gallegos", "America/Argentina/Salta", "America/Argentina/San_Juan", "America/Argentina/San_Luis", "America/Argentina/Tucuman", "America/Argentina/Ushuaia", "America/Aruba", "America/Asuncion", "America/Atikokan", "America/Bahia", "America/Bahia_Banderas", "America/Barbados", "America/Belem", "America/Belize", "America/Blanc-Sablon", "America/Boa_Vista", "America/Bogota", …, "Pacific/Marquesas", "Pacific/Midway", "Pacific/Nauru", "Pacific/Niue", "Pacific/Norfolk", "Pacific/Noumea", "Pacific/Pago_Pago", "Pacific/Palau", "Pacific/Pitcairn", "Pacific/Pohnpei", "Pacific/Ponape", "Pacific/Port_Moresby", "Pacific/Rarotonga", "Pacific/Saipan", "Pacific/Tahiti", "Pacific/Tarawa", "Pacific/Tongatapu", "Pacific/Truk", "Pacific/Wake", "Pacific/Wallis"]

Hay otra información que puede necesitar:

var isDaylightSavingTime: Bool { return TimeZone.current.isDaylightSavingTime(for: Date()) }
print(isDaylightSavingTime) // true (in effect)

var daylightSavingTimeOffset: TimeInterval { return TimeZone.current.daylightSavingTimeOffset() }
print(daylightSavingTimeOffset)  // 3600 seconds (1 hour - daylight savings time)


var nextDaylightSavingTimeTransition: Date? { return TimeZone.current.nextDaylightSavingTimeTransition }    //  "Feb 18, 2017, 11:00 PM"
 print(nextDaylightSavingTimeTransition?.description(with: .current) ?? "none")
nextDaylightSavingTimeTransition   // "Saturday, February 18, 2017 at 11:00:00 PM Brasilia Standard Time\n"

var nextDaylightSavingTimeTransitionAfterNext: Date? {
    guard
        let nextDaylightSavingTimeTransition = nextDaylightSavingTimeTransition
        else { return nil }
    return TimeZone.current.nextDaylightSavingTimeTransition(after: nextDaylightSavingTimeTransition)
}

nextDaylightSavingTimeTransitionAfterNext  //   "Oct 15, 2017, 1:00 AM"

TimeZone - Documentación de Swift para desarrolladores de Apple

Xcode 8.2.1 • Swift 3.0.2

Locale.availableIdentifiers
Locale.isoRegionCodes
Locale.isoCurrencyCodes
Locale.isoLanguageCodes
Locale.commonISOCurrencyCodes

Locale.current.regionCode           // "US"
Locale.current.languageCode         // "en"
Locale.current.currencyCode         // "USD"
Locale.current.currencySymbol       // "$"
Locale.current.groupingSeparator    // ","
Locale.current.decimalSeparator     // "."
Locale.current.usesMetricSystem     // false

Locale.windowsLocaleCode(fromIdentifier: "pt_BR")                   //  1,046
Locale.identifier(fromWindowsLocaleCode: 1046) ?? ""                // "pt_BR"
Locale.windowsLocaleCode(fromIdentifier: Locale.current.identifier) //  1,033 Note: I am in Brasil but I use "en_US" format with all my devices
Locale.windowsLocaleCode(fromIdentifier: "en_US")                                   // 1,033
Locale.identifier(fromWindowsLocaleCode: 1033) ?? ""                                // "en_US"

Locale(identifier: "en_US_POSIX").localizedString(forLanguageCode: "pt")            // "Portuguese"
Locale(identifier: "en_US_POSIX").localizedString(forRegionCode: "br")              // "Brazil"
Locale(identifier: "en_US_POSIX").localizedString(forIdentifier: "pt_BR")           // "Portuguese (Brazil)"

TimeZone.current.localizedName(for: .standard, locale: .current) ?? ""              // "Brasilia Standard Time"
TimeZone.current.localizedName(for: .shortStandard, locale: .current) ?? ""         // "GMT-3
TimeZone.current.localizedName(for: .daylightSaving, locale: .current) ?? ""        // "Brasilia Summer Time"
TimeZone.current.localizedName(for: .shortDaylightSaving, locale: .current) ?? ""   // "GMT-2"
TimeZone.current.localizedName(for: .generic, locale: .current) ?? ""               // "Brasilia Time"
TimeZone.current.localizedName(for: .shortGeneric, locale: .current) ?? ""          // "Sao Paulo Time"

var timeZone: String {
    return TimeZone.current.localizedName(for: TimeZone.current.isDaylightSavingTime() ?
                                               .daylightSaving :
                                               .standard,
                                          locale: .current) ?? "" }

timeZone       // "Brasilia Summer Time"

Puede usar el siguiente código para obtener la zona horaria actual

 func getCurrentTimeZone() -> String{

         return TimeZone.current.identifier

  }

  let currentTimeZone = getCurrentTimeZone()
   print(currentTimeZone)

NSTimeZone *timeZone = [NSTimeZone localTimeZone];
NSString *tzName = [timeZone name];

El nombre será algo así como "Australia / Sydney" o "Europa / Lisboa".

Dado que parece que solo te importa el continente, eso podría ser todo lo que necesitas.

Swift 4, 4.2 y 5

var timeZone : String = String()

override func viewDidLoad() {
    super.viewDidLoad()
    timeZone = getCurrentTimeZone()
    print(timeZone)
}

func getCurrentTimeZone() -> String {
        let localTimeZoneAbbreviation: Int = TimeZone.current.secondsFromGMT()
        let items = (localTimeZoneAbbreviation / 3600)
        return "\(items)"
}