C :

#include <stdio.h>
struct whichday
{ int year;
  int month;
  int date;
}s[1];

int main()
{int i,mon[12]={31,0,31,30,31,30,31,31,30,31,30,31},day=0,day1=0;
 scanf("%d%d%d",&s[0].year,&s[0].month,&s[0].date);
 if(s[0].year%4==0&&s[0].year%100!=0||s[0].year%400==0)
	 mon[1]=29;
 else 
	mon[1]=28;
 
 for(i=0;i<s[0].month-1;i++)
	 day1+=mon[i];

 day=day1+s[0].date;
 printf("%d",day);

 return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
    int n,y,r,k,pd,nn,yy,rr;
    while(cin>>n>>y>>r)
    {
        if(n%4!=0)
            pd=0;
        else if(pd%400==0)
            pd=1;
        else if(pd%100==0)
            pd=0;
        else 
            pd=1;
        k=0;nn=n;yy=1;rr=0;
        while(nn!=n||yy!=y||rr!=r)
        {
            k++;
            rr++;
            if(rr==32)
            {
                yy++;
                rr=1;
            }
            if(rr==31 &&(yy==4||yy==6||yy==9||yy==11))
            {
                yy++;
                rr=1;
                }
            if(rr==30 && yy==2 && pd==1)
            {
                yy++;
                rr=1;
                }
            if(rr==29 && yy==2 && pd==0)
            {    
                yy++;
                rr=1;
            }
        }
        cout<<k<<endl;
    }
}

Java :

import java.util.Scanner;

public class Main
{
	public static void main(String args[])
	{
		Scanner in=new Scanner(System.in);
		int year=in.nextInt(),month=in.nextInt(),day=in.nextInt();
		int daycount=0,yearnum;
		int s[][]={{31,29,31,30,31,30,31,31,30,31,30,31},{31,28,31,30,31,30,31,31,30,31,30,31}};
		if((year%400==0)||(year%100!=0&&year%4==0))yearnum=0;
		else yearnum=1;
		for(int i=0;i<month-1;i++)daycount+=s[yearnum][i];
		daycount+=day;
		System.out.println(daycount);
	}
}

Python :

a =map(lambda x:int(x), raw_input().split())

y = a[0]
m =a[1]
d =a[2]
l = [31,28,31,30,31,30,31,31,30,31,30,31]
if (y %4 ==0 and y %100 !=0) or y%400 ==0:
    l[1]=29
s=0
for i in range(m-1):
    s +=l[i]
print s +d