C :

#include<stdio.h>
int Run(int y);
int year[2]={365,366};
int month[2][12]={31,28,31,30,31,30,31,31,30,31,30,31,31,29,31,30,31,30,31,31,30,31,30,31};
int main()
{
	int y,m,d,n=8113,i,j;
	n-=365-month[0][0]-month[0][1]-month[0][2]-month[0][3];
	for(i=1778;n>=year[Run(i)];i++)
		n-=year[Run(i)];
	for(j=0;n>=month[Run(i)][j];j++)
		n-=month[Run(i)][j];
	printf("%d-%02d-%02d\n",i,j+1,n-1);
}
int Run(int y)
{
	if(y%4!=0||(y%100==0&&y%400!=0))
		return 0;
	else
		return 1;
}