24H Clock in C

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>	
#include <time.h>
 
void clock(void);
 
int main(void) {
	clock();
	return 0;
}
 
void clock(void) {
	int s, m, h;
 
	system("color F5");
 
	time_t rawtime;
	struct tm * timeinfo;
	char buffer_s [80];
	char buffer_m [80];
	char buffer_h [80];
	time ( &rawtime );
	timeinfo = localtime ( &rawtime );
	strftime (buffer_s,80,"%S",timeinfo);
	strftime (buffer_m,80,"%M",timeinfo);
	strftime (buffer_h,80,"%H",timeinfo);
 
	s = atoi(buffer_s)+1;
	m = atoi(buffer_m);
	h = atoi(buffer_h);
 
	printf("%d:%d:%d", h,m,s);
 
	while ( s < 61 ) {
		system("cls");
		if ( s == 60 ) {
			++m;
			s = 0;
			if ( m == 60 ) {
				m = 0;
				++h;
				if ( h == 24 ) {
					h = 0;
				}
			}
		} else {
			++s;
		}
		printf("%d:%d:%d", h,m,s);
		Sleep(1000);
	}
}