swift3.0系统时间的保存与比较

swift

1.保存系统当前时间

//MARK: -  获取当前时间转为字符串

class func saveCurrentTime() {

         let nowDate = NSDate()

         let formatter = DateFormatter()

         formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

         let dateString = formatter.string(from: nowDate as Date)

         UserDefaults.standard.set(dateString, forKey: "currentDate")

         UserDefaults.standard.synchronize() 

}

2.计算时间差(先转为时间戳在进行计算)

func fun_Interval() {

         //时间格式化

         let formatter = DateFormatter()

         formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

        //设置第一个时间戳

        let firstDateString = "2017-02-27 11:11:11"

        let firstDate = formatter.date(from: firstDateString)

        let firstInterval :TimeInterval = (firstDate?.timeIntervalSince1970)!

        //设置第二个时间戳

        let secondDateString = "2017-02-27 11:11:21"

        let secondDate = formatter.date(from: secondDateString)

        let secondInterval: TimeInterval = (secondDate?.timeIntervalSince1970)!

        let interval =  secondInterval - firstInterval

        print("interval = \(interval)")   //输出结果为10.0,计算的结果单位是S

}