// Declaring valid date character, minimum year and maximum year
var dtCh= "/";
var minYear=1900;
var maxYear=2100;

function validateOK()
{	
	 //global variables
	message = "";  //error message string
	dateerror = "";  //date error string
	timeerror = "";  //time error string

	//ensure a title has been entered
	if (document.forms[0].Title.value == "") 
	{
		message = "You must specify a Title" + "\n";
	}

	//check the start date	
	if (isDate(document.forms[0].StartDate.value)==false)
	{
		message =  message + "Your Start Date is not a valid date (" + dateerror + ")" + "\n";
	}

	//Check the start time
	if (IsValidTime(document.forms[0].StartTime.value)==false)
	{
		message = message + "The Start Time is not a valid time ( " + timeerror + ")" + "\n";
	}

	//Check the end time
	if (IsValidTime(document.forms[0].EndTime.value)==false)
	{
		message = message + "The End Time is not a valid time ( " + timeerror + ")" + "\n";
	}

	//stop the save and alert them if there are any errors
	if (message !="") 
	{
		alert ("Sorry, you cannot save this entry because of the following:" + "\n" + "\n" + message);
		return false;
	}

	return true;
}



function DaysArray(n) 
{
	for (var i = 1; i <= n; i++) 
	{
		this[i] = 31
		if (i==4 || i==6 || i==9 || i==11) 
		{
			this[i] = 30
		}

		if (i==2) 
		{
			this[i] = 29
		}
   	} 

   	return this
}

function daysInFebruary (year)
{

	// February has 29 days in any year evenly divisible by four,
    	// EXCEPT for centurial years which are not also divisible by 400.
    	return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}

function isInteger(s)
{
	var i;
	for (i = 0; i < s.length; i++)
	{   
		// Check that current character is number.
       		 var c = s.charAt(i);
        		if (((c < "0") || (c > "9"))) 
		{
			return false;
		}
	}

   	// All characters are numbers.
    	return true;
}
function isTelNumber(s) 
{
	var i;

	for (i = 0; i < s.length; i++)
	{   
		// Check that current character is number or space.
       		 var c = s.charAt(i);
        		if ((c < "0" && c!=" ") || (c > "9" && c !=" ")) 
		{
			return false;
		}
	}

   	// All characters are numbers or space.
    	return true;
}
function stripCharsInBag(s, bag)
{
	var i;
    	var returnString = "";

   	// Search through string's characters one by one.
    	// If character is not in bag, append to returnString.
    	for (i = 0; i < s.length; i++)
	{   
        		var c = s.charAt(i);
        		if (bag.indexOf(c) == -1) 
		{
			returnString += c;
		}

    	}

    	return returnString;
}

function isDate(dtStr)
{

	var daysInMonth = DaysArray(12)
	var pos1=dtStr.indexOf(dtCh)
	var pos2=dtStr.indexOf(dtCh,pos1+1)
	var strDay=dtStr.substring(0,pos1)
	var strMonth=dtStr.substring(pos1+1,pos2)
	var strYear=dtStr.substring(pos2+1)
	strYr=strYear

	if (strDay.charAt(0)=="0" && strDay.length>1) 
	{
		strDay=strDay.substring(1)
	}

	if (strMonth.charAt(0)=="0" && strMonth.length>1) 
	{
		strMonth=strMonth.substring(1)
	}

	for (var i = 1; i <= 3; i++) 
	{
		if (strYr.charAt(0)=="0" && strYr.length>1) 
		{
			strYr=strYr.substring(1)
		}
	}
	month=parseInt(strMonth)
	day=parseInt(strDay)
	year=parseInt(strYr)
	if (pos1==-1 || pos2==-1)
	{
		dateerror = "The date format should be : dd/mm/yyyy"
		return false
	}
	if (month<1 || month>12)
	{
		dateerror = "Please enter a valid month"
		return false
	}
	if (day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month])
	{
		dateerror = "Please enter a valid day"
		return false
	}
	if (strYear.length != 4 || year==0 || year<minYear || year>maxYear)
	{
		dateerror = "Please enter a valid 4 digit year between "+minYear+" and "+maxYear
		return false
	}

	if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false)
	{
		dateerror = "Please enter a valid date"
		return false
	}

	return true
}

function IsValidTime(timeStr) 
{
	// Checks if time is in HH:MM:SS AM/PM format.
	// The seconds and AM/PM are optional.
	var timePat = /^(\d{1,2}):(\d{2})(:(\d{2}))?(\s?(AM|am|PM|pm))?$/;

	var matchArray = timeStr.match(timePat);

	if (matchArray == null) 
	{
		timeerror = "Time is not in a valid format";
		return false;
	}

	hour = matchArray[1];
	minute = matchArray[2];
	second = matchArray[4];
	ampm = matchArray[6];

	if (second=="") 
	{ 
		second = null; 
	}

	if (ampm=="") 
	{ 
		ampm = null 
	}

	if (hour < 0 || hour > 23) 
	{
		timeerror = "Hour must be between 1 and 12. (or 0 and 23 for military time";
		return false;
	}

	if (hour <= 12 && ampm == null) 
	{
	}

	if  (hour > 12 && ampm != null) 
	{
		timeerror = "You can't specify AM or PM for military time";
		return false;
	}

	if (minute<0 || minute > 59) 
	{
		timeerror = "Minute must be between 0 and 59";
		return false;
	}

	if (second != null && (second < 0 || second > 59)) 
	{
		timeerror = "Second must be between 0 and 59";
		return false;
	}
}