Code:

#include <stdio.h>
long time(int, int, int);
int main()
{
int h1, h2, m1, m2, s2, s1, sentinel = 1;
while (sentinel == 1) {
scanf("%d%d%d", &h1, &m1, &s1);
if (h1 > 24 || h1 < 0 || m1 > 59 || m1 < 0 || s1 > 59 || s1 < 0) {
printf("Time is out of range\n");
continue;
}
scanf("%d%d%d", &h2, &m2, &s2);
if (h2 > 24 || h2 < 0 || m2 > 59 || m2 < 0 || s2 > 59 || s2 < 0) {
printf("Time is out of range\n");
continue;
}
/* ------------ Why isn't the following if statement allowed?---------*/
if ( !( h2 >= 12 && h1 >= 12 || h2 <= 12 && h1 <= 12 ) ) {
printf("The two times must be in the same twelve hour cycle\n");
continue;
}
if ( time(h1, m1, s1) > time(h2, m2, s2) ) {
/* Test statement */
printf("time1: %d time2: %d", time(h1, m1, s1), time(h2, m2, s2) );
printf("%d\n", time(h1, m1, s1) - time(h2, m2, s2) );
}
else {
/* Test Statement */
printf("time1: %d time2: %d", time(h1, m1, s1), time(h2, m2, s2) );
printf("%d\n", time(h2, m2, s2) - time(h1, m1, s1) );
}
}
return 0;
}
long time(int hours, int minutes, int seconds)
{
return hours % 12 * 3600 + minutes * 60 + seconds;
}