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

#define BASE_CENTURY           1900
#define BASE_YEAR              1970
#define DAYS_UPTO_1970       719469

#define SECONDS_PER_MINUTE       60
#define MINUTES_PER_HOUR         60
#define HOURS_PER_DAY            24
#define DAYS_PER_WEEK             7
#define DAYS_PER_YEAR           365
#define MIN_DAYS_PER_MONTH       28
#define AVG_DAYS_PER_MONTH       30
#define MAX_DAYS_PER_MONTH       31
#define MONTHS_PER_YEAR          12

#define ONE_SECOND                1
#define ONE_MINUTE     (SECONDS_PER_MINUTE * ONE_SECOND)
#define ONE_HOUR       (MINUTES_PER_HOUR   * ONE_MINUTE)
#define ONE_DAY          (HOURS_PER_DAY    * ONE_HOUR)
#define ONE_WEEK          (DAYS_PER_WEEK   * ONE_DAY)
#define ONE_MONTH     (AVG_DAYS_PER_MONTH  * ONE_DAY)
#define ONE_YEAR          (DAYS_PER_YEAR   * ONE_DAY)

int main(int argc, char *argv[])
{
	int stopYear = 2019;
	time_t current = 0;
	struct tm *when;
	struct tm start;

	start.tm_sec   =  0;
	start.tm_min   =  0;
	start.tm_hour  =  0;
	start.tm_mday  =  1;
	start.tm_mon   =  0;
	start.tm_year  = 1970 - BASE_CENTURY;
	start.tm_wday  =  0;
	start.tm_yday  =  0;
	start.tm_isdst =  0;

	if (argc > 1) {
		stopYear = atoi(argv[1]);
	}
	current = mktime(&start);
	do {
		when = gmtime(&current);
		printf("%4d %02d %02d = %d\n", when->tm_year + BASE_CENTURY, when->tm_mon + 1, when->tm_mday, when->tm_wday);
		current += ONE_DAY;
	}
	while (when->tm_year + BASE_CENTURY < stopYear);

	return 0;
}