Data.cpp

class Data {
	protected:
	int day_, month_, year_;
	bool valid_;
	
	bool isLeapYear(int year)
	{
		return year % 4 == 0;
	}
	
	int daysNumberForMonth(int month, int year)
	{
		switch(month)
		{
			case 4:
			case 6:
			case 9:
			case 11:
				return 30;
			
			case 2:
				return isLeapYear(year) ? 29 : 28;
			
			default:
				return 31;
		}
	}
	
	int getDayOfYear()
	{
		int days = day_;
		
		for(int i = 1; i < month_; i++)
		{
			days += daysNumberForMonth(month_, year_);
		}
		
		return days;
	}
	
	bool validateDate(int day, int month, int year)
	{
		if(month < 1 && month > 12) // Invalid month
			return false;
		
		if(day < 1 && day > daysNumberForMonth(month, year)) // Invalid day
			return false;
		
		return true;
	}
	
	public:
	void set(int day, int month, int year)
	{
		valid_ = validateDate(day, month, year);
		
		day_ = day;
		month_ = month;
		year_ = year;
	}
	
	bool isChristmas()
	{
		return day_ == 25 && month_ == 12;
	}
	
	int diff(Data other)
	{
		int days = 0, start, end;
		int dayOfYear = getDayOfYear();
		int otherDayOfYear = other.getDayOfYear();
		
		if(other.year_ >= year_)
		{
			if(other.year_ == year_ && otherDayOfYear < dayOfYear)
			{
				days = dayOfYear - otherDayOfYear;
			}
			else
			{
				days = otherDayOfYear - dayOfYear;
			}
			start = year_;
			end = other.year_;
		}
		else
		{
			days = dayOfYear - otherDayOfYear;
			start = other.year_;
			end = year_;
		}
		
		for(; start < end; start++)
		{
			days += isLeapYear(start) ? 366 : 365;
		}
		
		return days;
	}
};