MKTIME always return -1 (Window10_64bit / MSVS2019 / C++)

Question

I have problem.. I can not understand why Function MKTIME always return -1

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

using namespace std;

    int main() {
    time_t now = time(NULL);
    struct tm today;

    localtime_s(&today, &now);
    today.tm_year += 1900;
    today.tm_mon += 1;
    time_t t_today = mktime(&today);

    printf("%ld", (long)t_today);

    return 0;
}

t_today is -1

Answer 1

mktime can deal with only upto the year 3000. Adding 1900 to today.tm_year will exceed this limit. (1970 + 1900 = 3870) Try smaller offset.

References:

• localtime_s, _localtime32_s, _localtime64_s | Microsoft Docs
• mktime, _mktime32, _mktime64 | Microsoft Docs