// variable global a la que se puede acceder desde Javascript
var fecha_correcta = "";

	function isDateString(stringValue) {

		// this function is designed to mimic the "date" portion of the
		// VBScript IsDate() function, allowing dates to be validated
		// with JavaScript in browsers before you run into a problem
		// in ASP pages with date database columns or the VBScript
		// CDate() function; an exception is that string months
		// ("Jan," etc.) are not accepted
		
		// this function does not handle BC dates or dates past 12/31/9999
		
		// you obviously want to strip the comments from production scripts
		
		// create a String object
		var theString = new String(stringValue);
		
		// determine the delimiter character (must be "/" "-" or space)
		var delimiterCharacter
		if ( theString.indexOf('/') > 0 )
			delimiterCharacter = '/';
		else
			if ( theString.indexOf('-') > 0 )
				delimiterCharacter = '-';
			else
				if ( theString.indexOf(' ') > 0 )
					delimiterCharacter = ' ';
				else
					return false;
					
		// split the string into an array of tokens
		var theTokens = theString.split(delimiterCharacter);
		
		// there must be either two or three tokens
		if ( theTokens.length < 2 || theTokens.length > 3 )
			return false;
		
		// convert the tokens to String objects, which will be needed later,
		// stripping a single leading 0
		var tokenIndex, fecha, ano;
		for ( tokenIndex = 0; tokenIndex < theTokens.length; tokenIndex++ ) {
			theTokens[tokenIndex] = new String(theTokens[tokenIndex])			
			if ( theTokens[tokenIndex].charAt(0) == '0' )
				theTokens[tokenIndex] = theTokens[tokenIndex].substring(1, theTokens[tokenIndex].length);
		}

		// si el 3.er token existe es el año y si está en formato de 2 dígitos (aa) se
		// convierte a 4 díg. (aaaa)
		if ( theTokens.length > 2 )
		{
			ano = parseInt(theTokens[2]);
			if ( ano < 100 )
			{
				ano = 2000 + parseInt(theTokens[2]);
				theTokens[2] = ano.toString();
			}
		}
		else
		{
			fecha = new Date();
			theTokens[2] = fecha.getFullYear().toString();
		}
		
		// all of the tokens must be positive integers
		for ( tokenIndex = 0; tokenIndex < theTokens.length; tokenIndex++ ) {
			if ( ! isNonnegativeInteger(theTokens[tokenIndex]) )
				return false;
		}
		
		// we need to identify the year, month, and day tokens
		var numericValue;
		var yearTokenIndex = -1;
		var monthTokenIndex = -1;
		var dayTokenIndex = -1;
		for ( tokenIndex = 0; tokenIndex < theTokens.length; tokenIndex++ ) {
					
			// convert the value
			numericValue = parseInt(theTokens[tokenIndex], 10);
					
			// could this token be a month?
			if ( numericValue <= 12 ) {
					
				// yes; do we already have a month?
				if ( monthTokenIndex == -1 ) {
						
					// no; assign this token to the month and continue
					monthTokenIndex = tokenIndex;
					continue;
				}
				else {
							
					// we already have a month; this token could
					// also be the day; do we already have a day?
					if ( dayTokenIndex == -1 ) {
						
						// no; assign this token to the day and continue
						dayTokenIndex = tokenIndex;
						continue;
					}
					else {
							
						// we already have a day; this token could
						// also be the year; do we alreay have a year?
						if ( yearTokenIndex == -1 ) {
						
							// no; assign this token to the year and continue
							dayTokenIndex = tokenIndex;
							continue;
						}
					}
				}
			}
			else {
						
				// the value is too large for a month;
				// could this token be a day?
				if ( numericValue <= 31 ) {
						
					// yes; do we already have a day?
					if ( dayTokenIndex == -1 ) {
						
						// no; assign this token to the day and continue
						dayTokenIndex = tokenIndex;
						continue;
					}
					else {
							
						// we already have a day; this token could
						// also be the year; do we alreay have a year?
						if ( yearTokenIndex == -1 ) {
						
							// no; assign this token to the year and continue
							dayTokenIndex = tokenIndex;
							continue;
						}
					}
				}
				else {
						
					// the value is too large for a day;
					// could this token be a year?
					if ( numericValue <= 9999 ) {
					
						// yes; do we already have a year?
						if ( yearTokenIndex == -1 ) {
						
							// no; assign this token to the year
							yearTokenIndex = tokenIndex;
						}
					}
				}
			}
		}	// end of for loop
		
		// evaluate, based on the number of tokens
		if ( theTokens.length == 2 ) {
			
			// two tokens can be either a month/year combination or a month/day
			// combination with the current year assumed; either way, we must have
			// a month
			if ( monthTokenIndex == -1 )
				
				// no month
				return false;
				
			// do we have a year?
			if ( ! (yearTokenIndex == -1) ) {
			
				// yes; month/year combination; must be okay
				fecha_correcta = theTokens[0] + "-" + theTokens[1] + "-" + theTokens[2];
				return true;
			}
			else
				
				// no year; do we have a day?
				if ( ! (dayTokenIndex == -1) ) {
				
					// yes; month/day combination; get the current year
					var today = new Date();
					var currentYear = today.getYear();

					// make sure it's a valid date (we were testing days using
					// 31, and that might be too many for the month)
					return isDate(currentYear, theTokens[monthTokenIndex], theTokens[dayTokenIndex]);
				}
				else
				
					// we have neither a year nor a day
					return false;
		}
		else {
			
			// three tokens; we should have found tokens for year, month, and day
			if ( yearTokenIndex == -1 || monthTokenIndex == -1 || dayTokenIndex == -1 )
				
				// missing one or more
				return false;
			else
				
				// found all; however, VBScript can only handle the following sequences
				if ( monthTokenIndex == 0 ) {
				
					// must be m/d/y
					if ( dayTokenIndex != 1 || yearTokenIndex != 2)
						return false;
				}
				else
					if ( dayTokenIndex == 0 ) {
				
						// must be d/m/y
						if ( monthTokenIndex != 1 || yearTokenIndex != 2)
							return false;
					}
					else
						if ( yearTokenIndex == 0 ) {
				
							// must be y/m/d
							if ( monthTokenIndex != 1 || dayTokenIndex != 2)
								return false;
						}
						else
						
							// something is wrong
							return false;
				
				// make sure it's a valid date (we were testing days using a value
				// of 31, and that might be too many for the actual month)
				fecha_correcta = theTokens[0] + "-" + theTokens[1] + "-" + theTokens[2];
				return isDate(theTokens[yearTokenIndex], theTokens[monthTokenIndex], theTokens[dayTokenIndex]);
		}
	}

	function isTimeString(stringValue) {

		// this function is designed to mimic the "time" portion of the
		// VBScript IsDate() function, allowing times to be validated
		// with JavaScript in browsers before you run into a problem
		// in ASP pages with date database columns or the VBScript
		// CDate() function
		
		// you obviously want to strip the comments from production scripts
		// and place this function in the library file

		// create a String object
		var theString = new String(stringValue);
		
		// the string must have either two (hours and minutes) or three
		// (hours, minutes and seconds) tokens, delimited by ":";
		// split the string into an array of tokens
		var theTokens = theString.split(':');
		if ( theTokens.length < 2 || theTokens.length > 3 )
			return false;
		
		// convert the tokens to String objects, which will be needed later,
		// stripping whitespace
		var firstToken = new String(theTokens[0])
		firstToken = trim(firstToken);
		var middleToken;
		if ( theTokens.length == 3 ) {
			middleToken = new String(theTokens[1])
			middleToken = trim(middleToken);
		}
		var lastToken = new String(theTokens[theTokens.length - 1])
		lastToken = trim(lastToken);

		// the first token (hours) must be an integer between 0 and 23
		if ( ! isInteger(firstToken) )
			return false;
		if ( ! isIntegerInRange(firstToken, 0, 23) )
			return false;
		
		// are there three tokens?
		if ( theTokens.length == 3 ){
		
			// the middle token (minutes) must be an integer between 0 and 59
			if ( ! isInteger(middleToken) )
				return false;
			if ( ! isIntegerInRange(middleToken, 0, 59) )
				return false;
		}
			
		// the first one or two characters of the last token (either minutes
		// and optional am/pm indicator or seconds and am/pm indicator) must
		// be digits
		if ( ! isDigit(lastToken.charAt(0)) )
			return false;
		
		// the first character is a digit; split the last token into the minutes
		// or seconds value and the indicator; depending on the second character
		var lastValue;
		var ampmIndicator;
		if ( isDigit(lastToken.charAt(1)) ) {
			lastValue = new String(lastToken.substring(0, 2));
			if ( lastToken.length >= 3 )
				ampmIndicator = new String(trim(lastToken.substring(2, lastToken.length)));
			else
				ampmIndicator = new String();
		}
		else {
			lastValue = new String(lastToken.substring(0, 1));
			if ( lastToken.length >= 2 )
				ampmIndicator = new String(trim(lastToken.substring(1, lastToken.length)));
			else
				ampmIndicator = new String();
		}
		ampmIndicator = ampmIndicator.toUpperCase();
		
		// the last value must be between 0 and 59
		if ( ! isIntegerInRange(lastValue, 0, 59) )
			return false;
		
		// check the am/pm indicator, if there is one
		if ( ampmIndicator.length > 0 )
			if ( ! ( ampmIndicator == "AM" || ampmIndicator == "PM" ) )
				return false;
				
		// valid time
		return true;
	}

	// most of the following was derived from Netscape's FormChek.js
	// library, which should be reviewed for documentation and comments

	var daysInMonth = makeArray(12);
	daysInMonth[1] = 31;
	daysInMonth[2] = 29;
	daysInMonth[3] = 31;
	daysInMonth[4] = 30;
	daysInMonth[5] = 31;
	daysInMonth[6] = 30;
	daysInMonth[7] = 31;
	daysInMonth[8] = 31;
	daysInMonth[9] = 30;
	daysInMonth[10] = 31;
	daysInMonth[11] = 30;
	daysInMonth[12] = 31;

	var whitespace = " \t\n\r";

	function charInString(c, s) {
		for (i = 0; i < s.length; i++) {
			if (s.charAt(i) == c)
				return true;
	    }
	    return false
	}

	function daysInFebruary(year) {
	    return ( ((year % 4 == 0) && ((!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
	}

	function isDate(year, month, day) {
	    if ( ! ( isYear(year) && isMonth(month) && isDay(day) ) ) return false;
	    var intYear = parseInt(year);
	    var intMonth = parseInt(month);
	    var intDay = parseInt(day);
	    if ( intDay > daysInMonth[intMonth] ) return false; 
	    if ( ( intMonth == 2 ) && ( intDay > daysInFebruary(intYear) ) ) return false;
	    return true;
	}

	function isDay(s) {
	    return isIntegerInRange(s, 1, 31);
	}

	function isDigit(c) {
		return ( ( c >= "0" ) && ( c <= "9" ) )
	}

	function isInteger(s) {
		var i;
	    for ( i = 0; i < s.length; i++ )
	    {   
	        var c = s.charAt(i);
	        if ( ! isDigit(c) ) return false;
	    }
	    return true;
	}

	function isIntegerInRange(s, a, b) {
	    if ( ! isInteger(s) ) return false;
	    var num = parseInt (s);
	    return ( ( num >= a ) && ( num <= b ) );
	}

	function isMonth(s) {
	    return isIntegerInRange (s, 1, 12);
	}

	function isNonnegativeInteger(s) {
	    return ( isSignedInteger(s) && ( parseInt(s) >= 0 ) );
	}

	function isSignedInteger(s) {
	    var startPos = 0;
	    if ( ( s.charAt(0) == "-" ) || ( s.charAt(0) == "+" ) )
	       startPos = 1;    
	    return ( isInteger(s.substring(startPos, s.length)) )
	}

	function isYear(s) {
		if ( ! isNonnegativeInteger(s) ) return false;
	    return ( (s.length == 2) || (s.length == 4) );
	}

	function lTrim(s) {
		var i = 0;
	    while ( (i < s.length) && charInString(s.charAt(i), whitespace) )
	       i++;
	    return s.substring(i, s.length);
	}

	function makeArray(n) {
	   for ( var i = 1; i <= n; i++ ) {
	      this[i] = 0
	   } 
	   return this
	}

	function rTrim(s) {
		var i = 0;
	    while ( (i < s.length) && charInString(s.charAt(i), whitespace) )
	       i++;
	    return s.substring(i, s.length);
	}

	function trim(s) {
		return lTrim(rTrim(s));
	}
	function FechaBuena(parametro,formulario)
	// valida la fecha que está en el INPUT o elemento del formulario pasado como parámetro
	{
		if(document.forms(formulario).elements(parametro).value!="")
		{
			if (isDateString(document.forms(formulario).elements(parametro).value)==false)
			{
				alert("Fecha incorrecta. Debe ser de la forma dd/mm/aaaa");
				document.forms(formulario).elements(parametro).focus();
			}
			else
			{
				document.forms(formulario).elements(parametro).value = fecha_correcta;
			}
		}
	}