The getclock function sets the current value of the clock
    specified by clktyp into the location pointed to by tp.

    The clktyp argument is given as a symbolic constant name,
    as defined in the <timers.h> header file. Only the TIMEOFDAY
    symbolic constant, which specifies the normal time-of-day clock
    to access for systemwide time, is supported.

    For the clock specified by TIMEOFDAY, the value returned by
    this function is the elapsed time since the Epoch. The Epoch
    is referenced to 00:00:00 UTC (Coordinated Universal Time) 1 Jan
    1970.

    The getclock function returns a timespec structure, which is
    defined in the <timers.h> header file as follows:

     struct  timespec {

      unsigned long  tv_sec   /* Elapsed time in seconds since the Epoch*/
      long           tv_nsec  /* Elapsed time as a fraction of a second */
                              /* since the Epoch (in nanoseconds)       */

     };