///now -> string yyyy-MM-dd     2016-12-09
func dateNowAsString() -> String {
    
    let nowDate = Date()
    let timeZone = TimeZone.init(identifier: "UTC")
    let formatter = DateFormatter()
    formatter.timeZone = timeZone
    formatter.locale = Locale.init(identifier: "zh_CN")
    formatter.dateFormat = "yyyy-MM-dd HH:mm"
    
    let date = formatter.string(from: nowDate)
    return date.components(separatedBy: " ").first!
}