Quick and Dirty Calendar Functions

var DAYS = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];


function is_leap_year(y)
	{
		if((y % 4) != 0)
			return false;
			
		if((y % 100) == 0 && ((y % 400) != 0))
			return false;
			
		return true;
	}
	
	function get_day_of_week(m, d, y)
	{
		m = parseInt(m, 10);
		d = parseInt(d, 10);
		y = parseInt(y, 10);
		
		if(m > 12 || m < 1)
			throw "Month must be between 1 and 12";
			
		if(d > 31 || d < 1)
			throw "Day must be between 1 and 31";
			
		if(y < 1900)
			throw "Year must be greater than 1900";
			
		if((m == 4 || m == 6 || m == 9 || m == 11)	&& d > 30)
			throw "Day of month must be less than 30 for the months of April, June, September, and November";
		
		if(m == 2)
			if(is_yeap_year(y))
				if(d > 29)
					throw "Day must be less than 29 for a leap-year February";		
				else
					if(d > 28)
						throw "Day must be less than 28 for a common-year February";		
		
		var year = 1900;
		var month = 1;
		
		var days = 0;
		
		while (year < y)
		{		
			if(is_leap_year(year))
				days+= 366;
			else
				days+= 365;						
				
			year++;
		}
		
		while(month < m)
		{	
			if(month == 4 || month == 6 || month == 9 || month == 11)
				days += 30;
			else
			{
				if(month == 2)
				{
					if(is_leap_year(year))
						days += 29;
					else
						days += 28;
						
					console.log('!!!');
				}
				else
				{
					days += 31;
				}
			}
			
			month++;				
		}
		
		days += parseInt(d, 10);
		
		return DAYS[(days) % 7];
		
	}