Loop back after wrong input, problem with fgetc(stdin) and loop

Question

So i have this simple code that i've found here. I want to make it work in a loop. I've tried couple of times with diffrent methods but output is bad. Working in Ubuntu Visual Studio

EDIT I've added if(y>=2015 && y<=3000) and it is working properly?

EDIT 2 I've modified my code and followed @Sergey advice... It is still not working properly... I've tried to add "Check return value of scanf" but it is also not working.

        if ((scanf("%u", &d) == 1) && (scanf("%u", &m) == 1) && (scanf("%u", &y) == 1))
            while (fdateCheck());
        else
    //...EOF or conversion failure...
            while (fdateCheck());

or

while ((rc = scanf("%u.%u.%u", &d, &m, &y)) != EOF)
{
    if (rc != 3)
        //...oops data problems...
    else
        //...all OK...
}

Need advice about checking return of scanfs

int fdateCheck();

unsigned int d,m,y;
unsigned int daysinmonth[12]={31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int rc;
int legit = 0;

int main()
    {
        printf("Enter the date\n");
        scanf("%u.%u.%u",&d,&m,&y);
        while (fdateCheck());
    }
int fdateCheck()
    {   
        if (y % 400 == 0 || (y % 100 != 0 && y % 4 == 0))
            {
                daysinmonth[1]=29;
            }
            else if (y >= 2015 && y <= 3000)
                {
                    if (m < 13)
                        {
                            if (d <= daysinmonth[m-1])
                            legit = 1;
                        }

                    if (legit == 1)
                        {
                            system("clear");  
                            printf("It is a legitimate date!\n");
                            return 0;
                        }
                }
            else
                system("clear");     
                int ch = fgetc(stdin);
                if (ch == '\n')
                    {
                        system("clear");
                        printf("It's not a legitimate date!\n");
                        printf("\nRetry: ");
                        return 1;
                    }
                fflush(stdin);
    }

Answer 1

If you have an appropriate code in the function void main() and need to repeat it in a cycle as you describe you can do the following:

1. rename original void main() to int one_step()
2. put return 0; after printf("It is a legitimate date!\n");
3. put return 1; after printf("It's not a legitimate date!\n");
4. create the new void main() function as:

void main() {
    while(one_step());
}

You do not need break; and return main();. You may need some enhancements as described in the comments above. Good luck in coding!

UPDATE #1

I meant such an improvement of your code:

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

int fdateCheck();

int main()
{
    while (fdateCheck());
}

int fdateCheck()
{
int res;
int legit = 0;
unsigned int d,m,y;
unsigned int daysinmonth[12]={31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    // get input block
    printf("Enter the date\n");         // prompt for data
    res = scanf("%u.%u.%u",&d,&m,&y);   // get input data
    if (res == EOF) {                   // check if no more input
            printf("Input error\n");
            exit(1);
    }
    // check if input data is valid
    if (res != 3) {                     // check if 3 numbers scanned
            system("clear");
            printf("It is not a date\n");
            fflush(stdin);
            return 1;
    }
    // make leap year correction
    if (y % 400 == 0 || (y % 100 != 0 && y % 4 == 0)) {
        daysinmonth[1]=29;              // leap year correction
    }
    // check if year, month and day is valid
    if (y >= 2015 && y <= 3000) {       // check if year in this range
        if (0 < m && m < 13) {          // check if month in this range
            if (0 < d && d <= daysinmonth[m-1]) // check if day in this range
                legit = 1;
        }
    }
    // print a message and finish the iteration
    if (legit == 1) {
        printf("It is a legitimate date!\n");
        return 0;
    }
    else {
        system("clear");
        printf("It's not a legitimate date!\n");
        printf("Please retry.\n");
        fflush(stdin);
        return 1;
    }
}

I also moved all variables inside the function. This will restore values of legit and daysinmonth[1] before each iteration.

UPDATE #2

My next proposal:

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

int fdateCheck();

int main()
{
    while (fdateCheck());
}

int fdateCheck()
{
int res;
int legit = 0;
unsigned int d,m,y;
unsigned int daysinmonth[12]={31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    // get input block
    printf("Enter the date\n");         // prompt for data
    res = scanf("%u.%u.%u",&d,&m,&y);   // get input data
    if (res == EOF) {                   // check if no more input
            printf("Input error\n");
            exit(1);
    }
    // check if input data is valid
    if (res != 3) {                     // check if 3 numbers scanned
            fgetc(stdin);               // remove a barrier
            system("clear");
            printf("It is not a date\n");
            fflush(stdin);
            return 1;
    }
    // make leap year correction
    if (y % 400 == 0 || (y % 100 != 0 && y % 4 == 0)) {
        daysinmonth[1]=29;              // leap year correction
    }
    // check if year, month and day is valid
    if (y >= 2015 && y <= 3000) {       // check if year in this range
        if (0 < m && m < 13) {          // check if month in this range
            if (0 < d && d <= daysinmonth[m-1]) // check if day in this range
                legit = 1;
        }
    }
    // print a message and finish the iteration
    if (legit == 1) {
        printf("It is a legitimate date!\n");
        return 0;
    }
    else {
        system("clear");
        printf("It's not a legitimate date!\n");
        printf("Please retry.\n");
        fflush(stdin);
        return 1;
    }
}