Calendar-like day calculator

Hello, I am working on something like Day calculator. Your input is how often does something happen (example: every 2 weeks). And it's gonna print out Dates in every month for whole year. I am looking for help please.

Code:

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


int year, month, daysInMonth, day, weekDay = 0, startingDay;
char *months[] = {"January","February","March","April","May","June","July","August","September","October","November","December"};
int monthDay[] = {31,28,31,30,31,30,31,31,30,31,30,31};
int monthMonth[] = {1,1,2,3,4,5,6,7,8,9,10,11,12};
int repeater;
int beginDay;
int monthNum;
bool first = true;


void start() {
    printf("Enter number of year\n");
    scanf("%d", &year);
}


int get_1st_weekday(int year) {
    day = (((year - 1) * 365) + ((year - 1) / 4 ) - ((year - 1) / 100) + ((year) / 400) + 1) % 7;
    return day;
}


void printCalendarD() {
    if ((year%4 == 0 && year%100 != 0) || year%400 == 0) {
        monthDay[1] = 29;
    }
    startingDay = get_1st_weekday(year);
    for (month = 0; month < 12; month++) {
        daysInMonth = monthDay[month];
        printf("\n\n----------------%s----------------\n", months[month]);
        printf("\n  Sun  Mon  Tue  Wed  Thu  Fri  Sat\n");
    for (weekDay = 0; weekDay<startingDay;weekDay++)
        printf("    ");
    for (day = 1; day <= daysInMonth; day++) {
        printf("%5d", day);


    if (++weekDay > 6) {
        printf("\n");
        weekDay = 0;
      }
      startingDay = weekDay;
    }
  }
}


void printCalendar() {
    for (month = 0; month < 12;) {
        daysInMonth = monthDay[month];
        if (first == true) {
                month++;
        for (day = beginDay; day <= daysInMonth; day++) {
          first = false;
          printf("%d.%d\n", day, monthMonth[month]);
          }
        }
        if (first == false) {
                month++;
        for (day = 1; day <= daysInMonth; day++) {
          printf("%d.%d\n", day, monthMonth[month]);
          }
        }
      }
}


int main()
{
    start();
    printCalendarD();
    printf("\n\n\n");
    printf("Enter repeater value: ");
    scanf("%d", &repeater);
    printf("The value of a repeater is %d.\n", repeater);
    printf("Enter number of beginning day: ");
    scanf("%d", &beginDay);
    printf("Day of the beginning is %d.\n", beginDay);
    printCalendar();


    printf("\n\n\n");
    return 0;
}

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