Values Realtime clock and timer functions use the number of seconds and nanoseconds since the Epoch. Although this method is precise and suitable for the machine, it is not meaningful for application users. If your application prints or receives time information from users, you will want to convert time data to a more readable format. If you use the time function to retrieve system time, the input and return values are expressed in elapsed seconds since the Epoch. Your application should define the format for both user input and output and then convert these time values for use by the program.
Applications can store the converted time values for future use.
Note that although these C routines use seconds as the smallest unit of time, they provide users with a readable format. When you pass the time in seconds to these functions, some functions return a pointer to a tm structure. This structure breaks down time into units such as hours, minutes, and seconds, and stores the data in the appropriate fields. The system maintains time by adding 976 microseconds at every clock interrupt. Unless accounted for, the additional .78 milliseconds every 50 milliseconds will result in a wrong calculation of the elapsed time as calculated by the program.