messy elasped time

#include<stdio.h>
#include<stdbool.h>

struct date{
    int month;
    int day;
    int year;
};

const char namesOfDay[7][3] =
{{'S','U','N'},
{'M','O','N'},
{'T','U','E'},
{'W','E','D'},
{'T','H','U'},
{'F','R','I'},
{'S','A','T'}};

int main(void){
    int getDifference(struct date, struct date);
    int findNumDay(struct date);

    struct date firstDate = {8,3,2004};
    struct date secondDate = {.month = 2, .day = 21, .year = 2005};
    int diff = getDifference(firstDate, secondDate);

    printf("The difference between first date and second date is: %i\n", diff);

    int dayNum = findNumDay(secondDate);
    printf("The day of first date is: %c%c%c", namesOfDay[dayNum][0], namesOfDay[dayNum][1], namesOfDay[dayNum][2]);

    return 0;
}

int findNumDay(struct date date){
    int findN(struct date);
    return (findN(date) - 621049) % 7;
}

int findN(struct date date){

    int f, g;
    int specialDate(struct date);

    if (date.month <= 2){
        f = date.year - 1;
        g = date.month + 13;
    }else{
        f = date.year;
        g = date.month + 1;
    }

    return 1461 * f / 4 + 153 * g / 5 + date.day + specialDate(date);
}

int getDifference(struct date firstDate, struct date secondDate){

    return findN(secondDate) - findN(firstDate);

}

int specialDate(struct date date){

    if (date.month >=2 && date.month <= 3){
        if (date.year == 1800 || date.year == 1900)
            return 1;
        else if (date.year == 1700 || date.year == 1800)
            return 2;
    }

    return 0;
}