let usDateFormat = DateFormatter.dateFormat(FromTemplate: "MMddyyyy", options: 0, locale: Locale(identifier: "en-US"))
//usDateFormat now contains an optional string "MM/dd/yyyy"
let gbDateFormat = DateFormatter.dateFormat(FromTemplate: "MMddyyyy", options: 0, locale: Locale(identifier: "en-GB"))
//gbDateFormat now contains an optional string "dd/MM/yyyy"
let geDateFormat = DateFormatter.dateFormat(FromTemplate: "MMddyyyy", options: 0, locale: Locale(identifier: "de-DE"))
//geDateFormat now contains an optional string "dd.MM.yyyy"
You can use it in following way to get the current format from device:
let currentDateFormat = DateFormatter.dateFormat(fromTemplate: "MMddyyyy", options: 0, locale: Locale.current)