Challenge described at https://www.thenewboston.com/forum/topic.php?id=5311

main.c

/* (c) 2015 Sebastian Ramadan                                            *
 * May you perish in court if this makes its way into turnitin software, *
 * ... for it is my intellectual property ;)                             *
 */

#include <stdint.h>
#include <stdio.h>

int main(int argc, char **argv) {
    uintmax_t y;
    if (argc <= 1 || sscanf(argv[1], "%ju", &y) != 1) {
        printf("Usage: %s year   (where year is an integer between 0 and %ju)\n", argc && argv[0] ? argv[0] : "./app", UINTMAX_MAX);
        return 0;
    }

    y--;
    puts((char *[]) { "Sunday",   "Monday"
                    , "Tuesday",  "Wednesday"
                    , "Thursday", "Friday"
                    , "Saturday" }[(1 + 5 * (y % 4) + 4 * (y % 100) + 6 * (y % 400)) % 7]);
}