Calender program in C++

#include
using namespace std;
#include "stdlib.h"
void main ()

{
int year=1;
int yearstart=0;
int century=0;
int monthstart=0;
int endofweek=0;
int monthdays[]= {31,28,31,30,31,30,31,31,30,31,30,31};
int dayon[]= {1,1,1,1,1,1,1,1,1,1,1,1};
int month;
int currentyear;
int currentmonth;
int daysincalendaryearpriortocalendarmonth;
int daysinwholeyearssince1800;
int totalnumdays;
int daysinmonth;
int numblankdays=0;
int day;
int start;
int startday;


cout<<"Enter a year between 1800 & 2100 for the calendar you wish to produce"<>year;

if (year<1800 || year>2100)
cout<<"not a valid year"<>month;

if (month<0 || month>12)
cout<<"not a valid month"<
if (month ==1)
cout<<" january,"<<" "< if (month ==2)
cout<<" february,"<<" "< if (month ==3)
cout<<" march,"<<" "< if (month ==4)
cout<<" april,"<<" "< if (month ==5)
cout<<" may,"<<" "< if (month ==6)
cout<<" june,"<<" "< if (month ==7)
cout<<" july,"<<" "< if (month ==8)
cout<<" august,"<<" "< if (month ==9)
cout<<" september,"<<" "< if (month ==10)
cout<<" october,"<<" "< if (month ==11)
cout<<" november,"<<" "< if (month ==12)
cout<<" december,"<<" "<
cout<<"Sun"<<" "<<"Mon"<<" "<<"Tue"<<" "<<"Wed"<<" "<<"Thu"<<" "<<"Fri"<<" "<<"Sat"<
if (month==1 || month==3 || month==5 || month==7 || month==8 || month==10 || month==12)
daysinmonth=31;

if (month==4 || month==6 || month==9 || month==11)
daysinmonth=30;

if (month==2 & ((year % 400==0) || (year %4==0 && year % 100 !=0)))
daysinmonth=29;

if (month==2 & ((year % 400!=0) || (year %4!=0 && year % 100 ==0)))
daysinmonth=28;

//find start day

// steps 4-7 get total number of days algorithm
//step 4
while (currentyear {
//step 5
if ((year % 400==0) || (year %4==0 && year % 100 !=0))

daysinwholeyearssince1800 += 366;
else
daysinwholeyearssince1800 += 365;