Computes the difference, in seconds, between the two times
    specified by the time1 and time2 arguments.

    Format

      #include  <time.h>

      double difftime  (time_t time2, time_t time1);

1 - Arguments

 time2

    A time value of type time_t.

 time1

    A time value of type time_t.

2 - Description

    The type time_t is defined in the <time.h> header file as
    follows:

    typedef unsigned long int time_t

3 - Return Value

    n                  time2 - time1 in seconds expressed as a
                       double.