void Date::advance(){
    day++;                          //first increment the day
    if(this->exceedsDaysInMonth())  //if it crosses over to the next month
    {
        day = 1;                    //the day becomes the first of next month
        month++;                    //increment month in that case
        if(month > 12)              //if it crosses over to the next year
        {
            month = 1;              //the month becomes the first month
            year++;                 //of the next year
        }
    }
}

#include <iostream>
#include <string>

const bool FALSE =false;
const bool TRUE = true;

using namespace std;


class Date
{
public:
    Date(int mm, int dd, int yy);            
    Date( ){month=1; day=1; year=1900;}                
    
    int GetDay();
    int GetMonth();
    int GetYear();
    int difference(Date &date2);
    
    void set_date(int mm, int dd, int yy);    
    void display_date();                    
                            
    bool is_equal(Date& );
    bool is_less_than(Date& );
    
private:
    int month;
    int day;
    int year;
    int exceedsDaysInMonth();
    int isLeapYear();
    void advance();
    string month2string();
                        
};



int main()
{
    int m, d, y, days_apart;
    char slash;
    Date First_Date, Second_Date;
    
    cout<<"This program gives the number of days between two dates."<<endl;
TESTING:
    cout<<"Please enter a date in the form xx/xx/xxxx"<<endl;
    
    cin>>m>>slash>>d>>slash>>y;
    
    First_Date.set_date(m, d, y);
    
    cout<<"First Date is:"<<endl;
    First_Date.display_date();
    cout<<endl;
    
    cout<<"Please enter a second date in the form xx/xx/xxxx"<<endl;
    
    cin>>m>>slash>>d>>slash>>y;
    Second_Date.set_date(m, d, y);
    
    cout<<"Second Date is:"<<endl;
    Second_Date.display_date();
    cout<<endl;
  
    if(First_Date.is_equal(Second_Date))
        cout<<"The first date you entered is the same as the second date."<<endl;
    else if(First_Date.is_less_than(Second_Date))
        cout<<"The first date you entered is earlier than the second date."<<endl;
    else
        cout<<"The first date you entered is later than the second date"<<endl;  
      
      
     // NEEDS work still ... crashes here ... *********************
    //days_apart = First_Date.difference(Second_Date);
    cout<<"The two days are "<< days_apart<<" days apart."<<endl;
    
    cin.clear();
    cin.sync();
goto TESTING;
    cin.get();  
    return 0;
}

int Date::exceedsDaysInMonth()
{
  int days[] = {31,28,31,30,31,30,31,31,30,31,30,31};
  if ( month < 1 || month > 12 || day > days[month-1])
     return false;
    
  return true;
}

// convert numeric month into string
string Date::month2string()
{
   string months[] = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
   if ( !exceedsDaysInMonth() )
   {
    if ( !(month < 1 || month > 12) )
       return months[month-1];
    else
       return "Unknown month";
   }
   else
       return "Unknown month";
}

// return TRUE if a year is leap
int Date::isLeapYear() // logic needs work ....
{
   if ( (year % 4) != 0 )
      return FALSE;
      
   if ( (year % 400) != 0 )
      return TRUE;

    if ( (year % 100) == 0 )
      return FALSE;
      
   return FALSE;
}

// validate and calculate next date /// needs work still .....
void Date::advance()
{
  int td, tm, ty;
  int days[] = {31,28,31,30,31,30,31,31,30,31,30,31};
  
  if ( year < 0 )
  {
       cerr <<year << " is not a valid year" << endl;
       cin.sync();
       cin.get();
       exit(1);
  }
  if ( exceedsDaysInMonth() )
  {
    if ( month == 2 && day == 29 )
    {
        if ( ! isLeapYear() )
        {
            cerr << year << " is not a leap year, so Feb doesn't have 29 days" << endl;
            cin.sync();
            cin.get();
            exit(1);
        }
    }
    else
    {
        cerr << "Bad day value month - " << month << " (" << month2string();
        cerr <<  ") doesn't have " << day << " days "<< endl;
        cin.sync();
        cin.get();
        exit(1);
    }
  }
  // calculate tommorow
  if ( month == 2 && day == 28 && isLeapYear() == 1)
  {
    td=day;
    tm=month;
    ty=year;
    td++;
  }
}

int Date::difference(Date &date2)
{
    int diff_days=0;
    while ( !(this->is_equal(date2)) )
    {
        this->advance();    
        diff_days++;    
    }
    return diff_days;
}

int Date::GetMonth()

{
    return month;
}

int Date::GetDay()
{
    return day;
}

int Date::GetYear()
{
    return year;
}

void Date::set_date(int mm, int dd, int yy)
{    
    month = mm;
    day = dd;
    year = yy;
}

void Date::display_date()
{    
    string name_of_month[12];
    
    name_of_month[0]="January";
    name_of_month[1]= "February";
    name_of_month[2]= "March";
    name_of_month[3]= "April";
    name_of_month[4]=  "May";
    name_of_month[5]= "June";
    name_of_month[6]= "July";
    name_of_month[7]= "August";
    name_of_month[8]= "September";
    name_of_month[9]= "October";
    name_of_month[10]= "November";
    name_of_month[11]= "December";
    
    cout <<  name_of_month[month-1]  <<  " "  <<  day  <<  ", "  << year;
}

bool Date::is_equal(Date& Second_Date)
{
    if (month==Second_Date.month && day==Second_Date.day && year==Second_Date.year)
        return true;
    return false;
}

bool Date::is_less_than(Date& Second_Date)
{
    if(year <= Second_Date.year)
        if(month <= Second_Date.month)
            if(day < Second_Date.day)
                return true;
    return false;    
}

#include<iostream>
#include<fstream>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<string>
#include<cstring>
#include<iomanip>

#define TRUE 1
#define FALSE 0
using namespace std;

class Date
{

private:
    int month;
    int day;
    int year;

public:
    
    
    Date(int mm, int dd, int yy);            
    Date( ){month=1; day=1; year=1900;}                
    
    int GetDay();
    int GetMonth();
    int GetYear();
  
    
   int isLeapYear();
   string month2string();
   int exceedsDaysInMonth();
   void advance();
    
    void set_date(int mm, int dd, int yy);    
    void display_date();                    
                            
    bool is_equal(Date& );
    bool is_less_than(Date& );
                          


};

int difference(Date date1, Date date2);


// Actual function Bodies


int Date::GetMonth()
{

return month;
}


int Date::GetDay()
{
return day;
}

int Date::GetYear()
{
return year;
}


void Date::set_date(int mm, int dd, int yy)
{    
month = mm;
day = dd;
year = yy;

}


int Date::exceedsDaysInMonth(){

if  (isLeapYear() == 0)
{
  int days[] = {31,28,31,30,31,30,31,31,30,31,30,31};
  if ( month < 1 || month > 12 || day > days[month-1])
     return TRUE;
  
  else
  
     return FALSE;

}
else
{
int days[] = {31,29,31,30,31,30,31,31,30,31,30,31};
if ( month < 1 || month > 12 || day > days[month-1])
     return TRUE;
else
return FALSE;
}}
// convert numeric month into string
string Date::month2string(){
   char *months[] = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
   if ( exceedsDaysInMonth() ) {
    if ( ! (month < 1 || month > 12) )
       return months[month-1];
    else
       return "Unknown month";
   }
   else
    return "Unknown month";
}
// return TRUE if a year is leap
int Date::isLeapYear(){
   if ( (year % 4)  != 0 ){
      return FALSE;
   }
   else if ( (year % 400)  != 0 ){
      return TRUE;
   }
   else if ( (year % 100)  == 0 ){
      return FALSE;
   }
   else
   {
      return FALSE;
   }
}

void Date::advance(){


    day++;                         //first increments the day
    
    
  
    if(this->exceedsDaysInMonth())  //if it crosses over to the next month
    {
        day = 1;                    //the day becomes the first of next month
        month++;                    //increment month in that case
        if(month > 12)              //if it crosses over to the next year
        {
            month = 1;              //the month becomes the first month
            year++;                 //of the next year
        }
    }
}



int difference(Date date1, Date date2)
{

int diff_days=0;
while (!(date1.is_equal(date2))){
diff_days++;

date1.advance();    
    
}
return diff_days;

}



void Date::display_date()
{    

string name_of_month[12];

name_of_month[0]="January";
name_of_month[1]= "February";
name_of_month[2]= "March";
name_of_month[3]= "April";
name_of_month[4]=  "May";
name_of_month[5]= "June";
name_of_month[6]= "July";
name_of_month[7]= "August";
name_of_month[8]= "September";
name_of_month[9]= "October";
name_of_month[10]= "November";
name_of_month[11]= "December";

cout <<  name_of_month[month-1]  <<  " "  <<  day  <<  ", "  << year;
return;
}

bool Date::is_equal(Date& Second_Date)
{

if ((month==Second_Date.month) && (day==Second_Date.day) && (year==Second_Date.year))
    {return true;}

else
    {return false;}
}

bool Date::is_less_than(Date& Second_Date)
{

if (year < Second_Date.year)
{
    return true;
}

else if ((month < Second_Date.month)&& (year == Second_Date.year))
{
    return true;
}
else if ((day < Second_Date.day)&& ((month < Second_Date.month) ||(month == Second_Date.month)) && ((year < Second_Date.year) ||(year == Second_Date.year)))
{    
    return true;
}

else
{    
    return false;
}    
}

// ------------------ Main Program---------------------------------

int main()
{

int m1, m2, d1, d2, y1, y2, index=0, diff_days= 0;
int mm1, mm2, dd1, dd2, yy1, yy2, days_apart;
char slash;
Date First_Date, Second_Date, earlier_date, later_date, date1, date2;  


cout<<"This program gives the number of days between two dates."<<endl;
cout<<"Please enter a date in the form xx/xx/xxxx"<<endl;

cin>>m1>>slash>>d1>>slash>>y1;

First_Date.set_date(m1, d1, y1);

cout<<"First Date is:"<<endl;
First_Date.display_date();
cout<<endl;

cout<<"Please enter a second date in the form xx/xx/xxxx"<<endl;

cin>>m2>>slash>>d2>>slash>>y2;
Second_Date.set_date(m2, d2, y2);

cout<<"Second Date is:"<<endl;
Second_Date.display_date();
cout<<endl;

if(First_Date.is_equal(Second_Date))
{  
    cout<<"The first date you entered is the same as the second date."<<endl;
    days_apart = difference(First_Date,Second_Date);
    
}

else if(First_Date.is_less_than(Second_Date))

{
  
    cout<<"The first date you entered is earlier than the second date."<<endl;
    days_apart = difference(First_Date,Second_Date);  
}

else if(!(First_Date.is_less_than(Second_Date)))
{    
  
    cout<<"The first date you entered is later than the second date"<<endl;
    days_apart = difference(Second_Date,First_Date);
    cout<<"The two days are "<< days_apart<<" days apart."<<endl;
    
}

cout<<"The two dates are "<< days_apart<<" days apart."<<endl;
    

return 0;
}

/*
    Could still use some more polish ...
    like crash proofing on bad input
    and validating the dates input, that they are real dates?
    (Also see in line comments... )
    but it now .... seems ...to give the right answers ...
    for leap years too ... :)
*/

#include<iostream>
//#include<fstream> // These are not used here ... //
//#include<cstdlib>
//#include<cctype>
//#include<cmath>
#include<string>
//#include<cstring>
//#include<iomanip>

#define debugging true // to switch in a working 'isLeapYear()'

using namespace std;

class Date
{
    
private:
    int month;
    int day;
    int year;
    
public:
    
    Date(int mm, int dd, int yy);            
    Date() { month=1; day=1; year=1900; }                
    
    int GetDay();
    int GetMonth();
    int GetYear();
    
    // some of these can be private, the ones NOT called 'outside' ... //***
    bool isLeapYear();
    string month2string(); //***
    bool exceedsDaysInMonth();//***
    void advance(); // could be private if 'difference' was part of class //***
    
    void set_date(int mm, int dd, int yy);    
    void display_date();                    
                            
    bool is_equal(Date& );
    bool is_less_than(Date& );
};

// helper function ....
int difference( Date &date1, Date &date2 ) // Why not part of class?
{
    int diff_days = 0;
    while ( !date1.is_equal(date2) )
    {
        diff_days++;
        date1.advance();    
    }
    return diff_days;
}



// Actual function Bodies

int Date::GetMonth()
{
    return month;
}

int Date::GetDay()
{
    return day;
}

int Date::GetYear()
{
    return year;
}

void Date::set_date(int mm, int dd, int yy)
{    
    month = mm;
    day = dd;
    year = yy;
}

bool Date::exceedsDaysInMonth()
{
    // moved here so not repeated in 'else' ...
    int days[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
    
    if( !isLeapYear() )
    {
        if ( month > 12 || day > days[month]) return true;    
        
        return false;
    }
    else // is leap year ... so need to handle case of month == Feb
    {
        if ( month == 2 && day == 29 ) //<-- the 'tricky' condition to get right
            return false;  
        if ( month > 12 || day > days[month] )
            return true;
            
        return false;
    }
}

// convert numeric month into string
string Date::month2string()  
{
    char *months[] =
    {"***", "Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
    if ( !exceedsDaysInMonth() ) // 'exceedsDaysInMonth()' can be 'private' ...
    {
        if ( month >= 1 && month <= 12 )
            return months[month];
        else
            return "Unknown month";
    }
    else
        return "Unknown month";
}

#if debugging  // BELOW is a working example ...
bool Date::isLeapYear()
{
    if (year%4 != 0) return false;  // not a leap year
    if (year%100 == 0 && year%400 != 0) return false; // not a leap year
    return true;
}

#else
// return true if a year is leapyear
bool Date::isLeapYear()
{
    if ( year%4 != 0 )
        return false; // it EXITS here 'false'
    if ( year % 400 != 0 )
        return true; // or .... HERE ... 'true'
        
    // once you get to here ...  both of your returns are 'false'
    // so onlu one EXIT woyuld be needed ... BUT IS your logic ok? See above ex.
    /*
    if ( year % 100 == 0 )
        return false;
    */

    return false; /// or HERE ... 'false'
}
#endif


void Date::advance()
{
    day++;                          //first increment the day
    if( this->exceedsDaysInMonth() )//if it crosses over to the next month
    {
        day = 1;                    //the day becomes the first of next month
        month++;                    //increment month in that case
        if(month > 12)              //if it crosses over to the next year
        {
            month = 1;              //the month becomes the first month
            year++;                 //of the next year
        }
    }
}

void Date::display_date()
{    
    string name_of_month[]=
    {
        "***", "January", "February", "March",  "April", "May", "June",
        "July", "August", "September", "October", "November", "December"
    };
    cout <<  name_of_month[month]  <<  " "  <<  day  <<  ", "  << year;
    return;
}
    
bool Date::is_equal( Date& Second_Date )
{
    if (
            month==Second_Date.month
            && day==Second_Date.day
            && year==Second_Date.year
        )
        return true;
    // if reach here ...
    return false;
}
    
bool Date::is_less_than( Date& Second_Date )
{    
    if( year < Second_Date.year) return true;
    if( year <= Second_Date.year && month < Second_Date.month ) return true;
    if(
        year <= Second_Date.year
        && month <= Second_Date.month  
        && day < Second_Date.day
       )  
        return true;
    // if reach here ...
    return false;  
}

// ------------------ Main Program---------------------------------

int main()
{
    // DON'T NEED all these ... can use some over again
    //int m1, m2, d1, d2, y1, y2, index=0, diff_days= 0;
    //int mm1, mm2, dd1, dd2, yy1, yy2, days_apart;

    int m, d, y; // These are all that you need ...
    int mm, dd, yy, days_apart;
    char slash;
    Date First_Date, Second_Date;  
    
    cout<<"This program gives the number of days between two dates."<<endl;
    
TESTING:
    cout<<"Please enter a date in the form mm/dd/yyyy : ";
    
    cin>>m>>slash>>d>>slash>>y;
    
    First_Date.set_date(m, d, y); // need to validate that this is a possible date
    
    cout<<"First Date is:"<<endl;
    First_Date.display_date();
    cout<<endl;
    
    cout<<"Please enter a second date in the form mm/dd/yyyy : ";
    
    cin>>m>>slash>>d>>slash>>y;
    Second_Date.set_date(m, d, y); // need to validate ...
    
    cout<<"Second Date is:"<<endl;
    Second_Date.display_date();
    cout<<endl;
    
    if(First_Date.is_equal(Second_Date))
    {  
        cout<<"The first date you entered is the same as the second date."<<endl;
        days_apart = difference(First_Date,Second_Date);
    }
    else if(First_Date.is_less_than(Second_Date))
    {
        cout<<"The first date you entered is earlier than the second date."<<endl;
        days_apart = difference(First_Date,Second_Date);  
    }
    
    else // the date can only be equal or less than ...or ELSE it is greater
    {    
        cout<<"The first date you entered is later than the second date"<<endl;
        days_apart = difference(Second_Date,First_Date);
        // cout<<"The two days are "<< days_apart<<" days apart."<<endl;
    }
    
    cout<<"The two dates are "<< days_apart<<" days apart.\n"
        <<".. or have " << days_apart+1 << " inclusive days between them.\n\n"
        << flush;
    
    cin.clear();
    cin.sync();
goto TESTING;

    cin.get();  
    return 0;
}

/*
Quick question, is the year 2000 a leap year? A suprising number of people give
the wrong answer. The correct answer is "yes", that is 2000 is a leap year.
Why do so many folks give the wrong answer to this simple question? In general,
a year is a leap year if it is evenly divisible by 4.
Most people also remember the exception which is a year is not a leap year if
it ends in "00" (ie., the year is even divisable by 100). So years like 1972,
1980, and 1996 are leap years, but 1800 and 1900 are not.

So why then is a 2000 a leap year? What many folks do not realize is that the
100 year exception itself has an exception. Years that are evenly divisable by
400 are leap years. So 2000 as well as 2400 will be leap years.

Programmers who write date conversion code and don't know about the "exception
to the exception" will end up creating software which will display incorrect
dates starting Feb. 29th, 2000. The incorrect conversions software will instead
give Feb. 29th as March 1. Even worse, all subsequent dates will likely be off
by one day also.

Although the Leap Year 2000 bug is not technically the same as the Y2K bug, it
is many times lumped together Y2K bug because it occurs so close to Jan. 1, 2000.

Over the years, operating systems and development tools have shipped with the
"Leap Year 2000" bug in them. This means that applications that use these broken
operating systems or tools will also have the bug. However, over the last 5
years with the all of the talk of the Y2K bug, most of the problems have been
fixed.

*/