IOS Swift set DateFormatter and Calendar with en_US_POSIX

SetEN_US_POSIX_IN_IOS.swift

func toGmtDate(year: Int, month: Int, date: Int, hour: Int, minute: Int, second: Int) -> Date? {
    let str = String(format: "%04d-%02d-%02d %02d:%02d:%02d+0800",
                     year, month, date,
                     hour, minute, second)
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ssZ"
    dateFormatter.locale = Locale(identifier: "en_US_POSIX") // Set locale to POSIX
    if let date = dateFormatter.date(from: str) {
        return date
    } else {
        return nil
    }
}

func convertDateToCalendar(date: Date) -> DateComponents {
    var calendar = Calendar(identifier: .gregorian)
    calendar.locale = Locale(identifier: "en_US_POSIX") // Set locale to POSIX
    if let timezone = TimeZone(identifier: "Asia/Taipei") {
        calendar.timeZone = timezone
    }
    let dateComponents = calendar.dateComponents([.year, .month, .day], from: date)
    return dateComponents
}