C :

#include <stdio.h>
#include <math.h>
int main(void){
	char month[20][20]={" ","January","February","March","April","May","June","July","August","September","October","November","December"};
	int n,i;
	int day,year;
	char M[20];
	int w,y,c;
	char week[7][10]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
	while (scanf("%d %s %d",&day,M,&year)!=EOF){
	for (i=1; i<13; i++){
		if (strcmp(M,month[i])==0){
			if(i<3){
				year-=1;
				i+=12;
			}
			break;
		}
		}
			c=year/100;
			y=year-100*c;
			w=(int)(c/4)-2*c+(int)(y+y/4)+(int)(13*(i+1)/5)+day-1;
			while(w<0){
				w+=7;
			}
			w=w%7;
			printf("%s\n",week[w]);
	}
	return 0;
}

C++ :

#include<cstdio>
#include<iostream>
#include<string>
using namespace std;

int weekday(int d,int m,int y)
{
	int tm=m>=3?(m-2):(m+10);
	int ty=m>=3?y:(y-1);
	return (ty+ty/4-ty/100+ty/400+(int)(2.6*tm-0.2)+d)%7;
}

int main()
{
	char week[][10]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
	int d,y,m;
	string M;
	while(cin>>d>>M>>y)
	{
		if(M=="January")
			m=1;
		else if(M=="February")
			m=2;
		else if(M=="March")
			m=3;
		else if(M=="April")
			m=4;
		else if(M=="May")
			m=5;
		else if(M=="June")
			m=6;
		else if(M=="July")
			m=7;
		else if(M=="August")
			m=8;
		else if(M=="September")
			m=9;
		else if(M=="October")
			m=10;
		else if(M=="November")
			m=11;
		else if(M=="December")
			m=12;
		printf("%s\n",week[weekday(d,m,y)]);
	}
	return 0;
}

Python :

# coding=utf-8
import datetime
Date = datetime.datetime

while True:
    date = Date.strptime(input(),"%d %B %Y")
    print(date.strftime("%A"))