Easy time interface, with clear names. You can also execute a function with any number of arguments in a determined interval.

easy-time.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#if defined(WIN32) || defined(_WIN32) || defined(__WIN32) && !defined(__CYGWIN__)
#include <windows.h>
#else
#include <unistd.h>
#define Sleep(time) sleep(time/1000)
#endif

#define MACRO void

MACRO setTimeout(int time, void (*function)(), ...) {}
#define setTimeout(time, function, ...) \
	Sleep(time); function(__VA_ARGS__);

MACRO setInterval(int condition, int time, void (*function)(), ...) {}
#define setInterval(condition, time, function, ...) \
	while (condition) {function(__VA_ARGS__); Sleep(time);}

MACRO printTime(clock_t start, clock_t end) {}
#define printTime(start, end) \
	(float)(end - start) / CLOCKS_PER_SEC	

#undef MACRO

typedef struct TIME {
	int day;
	int month;
	int year;
	int hour;
	int minute;
	int second;
	int wday;
	int yday;
	int is_day;
} Time;

void updateTime(Time *time_s) {
	
    if (time_s == NULL) return;
	
    time_t t;
    time(&t);
    struct tm *time_tm;
    time_tm = localtime(&t);
    time_tm->tm_mon += 1;
    time_tm->tm_year += 1900;	
	
    time_s->day			=	time_tm->tm_mday;
    time_s->month		=	time_tm->tm_mon;
    time_s->year		=	time_tm->tm_year;
    time_s->hour		=	time_tm->tm_hour;
    time_s->minute		=	time_tm->tm_min;
    time_s->second		=	time_tm->tm_sec;
    time_s->yday		=	time_tm->tm_yday;
    time_s->wday		=	time_tm->tm_wday;
    time_s->is_day		=	time_tm->tm_isdst;	
}

Time* createTime() {
    Time *time_s = (Time*)malloc(sizeof(Time));
    
    updateTime(time_s);
		
    return time_s;
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

Time *t;

void foobar(char *str) {
	updateTime(t);
	
	printf("%s\n", str);
}

int main() {
	clock_t start = clock();
	
	t = createTime();
	
	setInterval(t->second > 30, 1000 * 3, foobar, "foo");
	
	setInterval(t->second <= 30, 1000 * 3, foobar, "bar");
	
	free(t);
	
	clock_t end = clock();
	
	printf("%5.2fsec\n", printTime(start, end));		
}