Month calender in plain C

Program prints the month without using any system related information but just making some simple calculations of days from the reference day 1/1/1900 as Monday.

Code:

#include<stdio.h>
#include<conio.h>
#define Y 1900             /*1/1/1900 Monday*/

void days(int ,int );
void display(int , int );

// Almost constant but we modify the month[1] i.e. Feb for leap year
int month[]={{31},{28},{31},{30},{31},{30},{31},{31},{30},{31},{30},{31}};

int main()
{
	int m,yr;
	int i = 0;
	do
	{
		i++;
		if(i > 1)
		{
			printf("\nWhat kind of month that was please re-enter\n");
		}
		printf("Enter the month [1-12]\t");
		scanf("%ld",&m);
	}while(m>12 || m<0);
	i = 0;
	do
	{
		i++;
		if(i > 1)
		{
			printf("\nPlease enter year of this century i.e. 1900 or above\n");
		}
		printf("Enter the year\t");
		scanf("%ld",&yr);
	}while(yr<1900);

	if((yr%4==0)&&((yr%100!=0)||(yr%400==0)))
	{
		// We did not had the month as const because of this.
		month[1]=29;
	}

	days(m,yr);
	printf("\n\n");
	return 0;
}

void days(int m,int yr)
{
	int i,md=0,leap=0,track;
	unsigned int d,yrd;
	for(i=Y;i<yr;i++)
	{
		if((i%4==0)&&((i%100!=0)||(i%400==0)))
			leap++;
	}
	for(i=0;i<(m-1)&&(i<11);i++)
		md=md+month[i];
	yrd=(yr-Y)*365;
	d=yrd+leap+md;
	track=d%7;
	display(m,track);
}

void display(int m, int track)
{
	int dt,loop;
	printf("\n\n\t");
	printf("Mon\tTues\tWed\tThurs\tFri\tSat\tSun\n\n");
	for(loop=0;loop<=track;loop++) 
		printf("\t");
	for(dt=1;dt<=month[m-1];dt++)
	{
		if(track%7==0 && track!=0)
			printf("\n\n\t");
		printf("%d\t",dt);
		track++;
	}
}

Output

Code:

Enter the month [1-12]  4
Enter the year  2007


    Mon     Tues    Wed     Thurs   Fri     Sat     Sun

                                                    1

    2       3       4       5       6       7       8

    9       10      11      12      13      14      15

    16      17      18      19      20      21      22

    23      24      25      26      27      28      29

    30