//C program to calculate difference between two time periods
#include <stdio.h>
struct Time
{
  int secs;
  int mins;
  int hours;
};
void difference(struct Time t1, struct Time t2, struct Time *diff);
 
int main()
{
    struct Time startTime, stopTime, diff;
 
    printf("Please enter start time: \n");
    printf("Enter hours, minutes and seconds respectively: ");
    scanf("%d %d %d", &startTime.hours, &startTime.mins, &startTime.secs);
 
    printf("Please enter stop time: \n");
    printf("Enter hours, minutes and seconds respectively: ");
    scanf("%d %d %d", &stopTime.hours, &stopTime.mins, &stopTime.secs);

    difference(startTime, stopTime, &diff);
 
    printf("\nTIME DIFFERENCE: %d:%d:%d - ", startTime.hours, startTime.mins, startTime.secs);
    printf("%d:%d:%d ", stopTime.hours, stopTime.mins, stopTime.secs);
    printf("= %d:%d:%d\n", diff.hours, diff.mins, diff.secs);
 
    return 0;
}
 
void difference(struct Time start, struct Time stop, struct Time *diff)
{
    if(stop.secs > start.secs){
        --start.mins;
        start.secs += 60;
    }
 
    diff->secs = start.secs - stop.secs;
    if(stop.mins > start.mins){
        --start.hours;
        start.mins += 60;
    }
 
    diff->mins = start.mins - stop.mins;
    diff->hours = start.hours - stop.hours;
}