C Program to calculate the difference between two time periods

Enter the start and stop time with hours, minutes and seconds. Finally, we need to find the difference between start and stop time.

The logic to find the difference between start and stop time is given below −

while (stop.sec > start.sec){
   --start.min;
   start.sec += 60;
}
diff->sec = start.sec - stop.sec;
while (stop.min > start.min) {
   --start.hrs;
   start.min += 60;
}
diff->min = start.min - stop.min;
diff->hrs = start.hrs - stop.hrs;

Example

Following is the program to find difference between start and stop time −

 Live Demo

#include <stdio.h>
struct time {
   int sec;
   int min;
   int hrs;
};
void diff_between_time(struct time t1,
struct time t2,
struct time *diff);
int main(){
   struct time start_time, stop_time, diff;
   printf("Enter start time. 
");
   printf("Enter hours, minutes and seconds: ");
   scanf("%d %d %d", &start_time.hrs,
   &start_time.min,
   &start_time.sec);
   printf("Enter the stop time. 
");
   printf("Enter hours, minutes and seconds: ");
   scanf("%d %d %d", &stop_time.hrs,
   &stop_time.min,
   &stop_time.sec);
   // Difference between start and stop time
   diff_between_time(start_time, stop_time, &diff);
   printf("
time Diff: %d:%d:%d - ", start_time.hrs,
   start_time.min,
   start_time.sec);
   printf("%d:%d:%d ", stop_time.hrs,
   stop_time.min,
   stop_time.sec);
   printf("= %d:%d:%d
", diff.hrs,
   diff.min,
   diff.sec);
   return 0;
}
// Computes difference between time periods
void diff_between_time(struct time start,
struct time stop,
struct time *diff){
   while (stop.sec > start.sec) {
      --start.min;
      start.sec += 60;
   }
   diff->sec = start.sec - stop.sec;
   while (stop.min > start.min) {
      --start.hrs;
      start.min += 60;
   }
   diff->min = start.min - stop.min;
   diff->hrs = start.hrs - stop.hrs;
}

Output

When the above program is executed, it produces the following result −

Enter start time.
Enter hours, minutes and seconds: 12 45 57
Enter the stop time.
Enter hours, minutes and seconds: 20 35 20
time Diff: 12:45:57 - 20:35:20 = -8:10:37