利用NSDateFormatter类可以进行时间格式与时间戳之间的转化

:param: stringTime 时间为string

:returns: 返回时间戳为strings
*/
static func stringToTimeStamp(stringTime:String)->String {

    var dfmatter = NSDateFormatter()
    dfmatter.dateFormat="yyyy年MM月dd日"
    var date = dfmatter.dateFromString(stringTime)

    var dateStamp:NSTimeInterval = date!.timeIntervalSince1970

    var dateSt:Int = Int(dateStamp)
    print(dateSt)
    return String(dateSt)

}

:param: timeStamp <#timeStamp description#>

:returns: return time
*/
static func timeStampToString(timeStamp:String)->String {

    var string = NSString(string: timeStamp)

    var timeSta:NSTimeInterval = string.doubleValue
    var dfmatter = NSDateFormatter()
    dfmatter.dateFormat="yyyy年MM月dd日"

    var date = NSDate(timeIntervalSince1970: timeSta)

    print(dfmatter.stringFromDate(date))
    return dfmatter.stringFromDate(date)
}