时间计算，操作系统时间函数调用,此函数为自写函数，没有操作系统函数的线程安全问题，如有此地方发操作系统转化函数不安全或有问题，可用引函数-Time calculation, the operating system time function call, this function is self-write function, there is no operating system functions thread safety issues, if any, made ​