Trying to get mm/dd/yy format

[ten_d]

Hi all,

I'm a total mega C++ newb.. I'm trying to figure out how to get a normal date that a user input from mm/dd/yyyy format to mm/dd/yy format.

Please help!! Thanks!

[ten_d]

This may help a bit. Here's my class so far.

//Date Class definition
#ifndef DATE1_H
#define DATE1_H
//#include <iostream>

class Date {

public:
Date( int = 1, int = 1, int = 1990); //defult constructor
void print() const; //print date in month/day/year format
void printJulian() const; //print in julian format ddd/yyyy
~Date();

private:
int month;
int day;
int year;

int checkDay(int) const;

}; //end of class Date
#endif

Date::Date(int mn, int dy, int yr)
{
cout << "Enter the month: ";
cin >> mn;
cout << "Enter the day: ";
cin >> dy;
cout << "Enter the year: ";
cin >> yr;

if (mn > 0 && mn <= 12)
month = mn;

else {
month = 1;
cout << "Month " << mn << " is invalid. Month is set to 1.\n";
}

year = yr;
day = checkDay(dy);

} //end Date constructor



//print Date object in form month/day/year
void Date::print() const
{
cout << "The day is " << month << '/' << day << '/' << year << endl;
} //end of function print

//output Date object to show when its destructor is called
Date::~Date()
{

} //end destructor ~Date



//utility function to confirm proper day value based on month and year, handles leap years too
int Date::checkDay(int testDay) const
{
static const int daysPerMonth[13] =
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

//determine whether testDay is valid for specified month
if (testDay > 0 && testDay <= daysPerMonth [month])
return testDay;

//Feb 29 check
if (month == 2 && testDay == 29 && (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)))
return testDay;

cout << "Day " << testDay << " is invalid. Date set to 1.\n";

return 1;
} //end of function checkDay



void Date::printJulian() const
{
static const int daysPerMonth[13] =
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

int julDate = day;

for (int counter =0; counter < month; counter++)
{
julDate = julDate + daysPerMonth[counter];
}

if ((year % 400 == 0 || (year % 4 ==0 && year % 100 != 0)) && (month >= 2 && day > 28))
julDate++;

cout << "The date in Julian style ddd/yyyy is " << julDate << '/' << year << endl;
} //end of printJulian function

[Valmont]

Date and time fuctions in MS Windows is one of the less trivial things I'm affraid.
But here is a nice approach:

#include <ctime>
#include <iostream>

using namespace std;

time_t timeDate;
struct tm *currDate;

int main()
{
	char yearBuffer[4];

	timeDate = time(0);
	currDate = localtime(&timeDate); //DOS systemcall!
		
	int month = currDate->tm_mon+1;
	int day = currDate->tm_mday;
        //int year = currDate->tm_year+1900; //Outputs: 2004 
	strftime( yearBuffer, 4, "%y", currDate ); //Output: 04 (instead of 2004)

	cout<<day<<" "<<month<<" "<<yearBuffer<<endl;

	return 0;
}

Just a little hint for the upcoming programmer FWIW:
The first thing is clarity. Check out this:

Date set to 1.

What is this?
Val: 'What is the date today?'
Alex: 'Today is 1'.
Val: 'Huh? What was the date of yesterday or the day before yesterday then?'
Alex: '...'

Do you see what I mean?
GL HF!

[Valmont]

If you don't have the time to check out the date libraries in C++ then here is your code revised.

- You definatly want to check out printShortYear():
It answers your question more directly. Look at the "itoa()" and the "string::assign()" function. Both of them come with the standard C++ library.

- I've taken the liberty to remove the comments:
It is obvious what these methods do, so lets not add them.
Certainly don't add comments for constructors. People should (and will) recognize constructors/destructors on-the-fly.

- I've removed the default values in your default ctor:
Default values in a default ctor takes away flexibility. Instead, I've added a ctor wich takes three arguments.

- I've broken certain algorithms in smaller parts.
This way there is no double code. It also makes the various methods more readable. Clearness is all.

Here is the complete code, a main function included to demonstrate it's workings:
In CDate.h

#ifndef CDATE_H
#define CDATE_H

#include <iostream>
#include <string>

using namespace std;

static const int daysPerMonth[13] = 
	{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

class Date 
{
public:
	Date() { GetDate(); ValidateDate(); } 
	Date(int mt, int dy, int yr) : month(mt), day(dy), year(yr) {	ValidateDate(); }
	~Date() { };
public:
	void print() const; 
	void printJulian() const;
	
private:
	int month;
	int day;
	int year;
	void GetDate();
	void ValidateDate();
	bool CheckValidDay();
	bool CheckForLeapYear() const;
	string printShortYear() const;
	void reset_istream(istream & is);
}; 

void Date::GetDate()
{	
retry_month: cout << "Enter the month: ";
	cin >> month; 
	if(cin.fail()) { reset_istream(cin); goto retry_month; return; }
retry_day: cout << "Enter the day: ";
	cin >> day;
	if(cin.fail()) { reset_istream(cin); goto retry_day; return; }
retry_year: cout << "Enter the year: ";
	cin >> year;	
	if(cin.fail()) { reset_istream(cin); goto retry_year; return; }
}

void Date::ValidateDate()
{
	if ((month > 0 && month <= 12)==false)
		{
			month = 1;
			cout << "Month is invalid. Month has been re-set to 1.\n";
		}	
	//Leapyear and valid day in current month.
	if(!CheckValidDay())
		{ cout<<"Day is invalid, day has been re-set to 1"<<endl; day =1; }
}

void Date::print() const
{	
	cout << "The date is " << month << '/' << day <<
		'/'<<printShortYear()<<endl; 
} 

void Date::printJulian() const
{	
	int julDate = day;
	for (int counter =0; counter < month; counter++)
		julDate = julDate + daysPerMonth[counter];	
	if ((year % 400 == 0 ||CheckForLeapYear() ) && (month >= 2 && day > 28))
		julDate++;

	cout <<"The date in Julian style ddd/yy is " << julDate << 
		'/'<<printShortYear()<< endl; 
} 

string Date::printShortYear() const
{
	char szYearBuffer[4];
	string sShortYear;
	itoa(year, szYearBuffer, 10);
	sShortYear.assign(szYearBuffer, 2, 2);
	return sShortYear;
}

bool Date::CheckForLeapYear() const
{	return (year % 4 ==0 && year % 100 != 0); }

bool Date::CheckValidDay() 
{
	if (!(day > 0 && day <= daysPerMonth [month]))
		return (month == 2 && day == 29 && CheckForLeapYear());	
	
	return true;
} 

void Date::reset_istream(istream & is)
{
	char ch;
	// Reset the state. 
	is.clear();
	// Remove all characters until we find a newline or EOF.
	ch = is.get();
	while ((ch != '\n')&&(ch != EOF))
		ch = is.get();	
	is.clear();
}

#endif //CDATE_H

Just ask if you need more help.

[Valmont]

Oops, I forgot the main() function:

#include "CDate.h"

int main()
{
	Date MyDate;
	MyDate.print();
	MyDate.printJulian();
	
	cout<<endl;

	Date MyOtherDate(2, 29, 2004);
	MyOtherDate.print();
	MyOtherDate.printJulian();
	
	return 0;
}