function isValidDate(dateStr) {

	var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{4})$/; // requires 4 digit year
	var matchArray = dateStr.match(datePat); // is the format ok?
	if (matchArray == null) {
		alert("El formato de la fecha no es valido.")
		return false;
	}
	
	month = matchArray[3]; // parse date into variables
	day = matchArray[1];
	year = matchArray[4];
	
	if (month < 1 || month > 12) { // check month range
		alert("El mes debe estar entre 1 y 12.");
		return false;
	}
	
	if (day < 1 || day > 31) {
		alert("El d»a debe estar entre 1 y 31.");
		return false;
	}
	
	if ((month==4 || month==6 || month==9 || month==11) && day==31) {
		alert("Este mes no tiene 31 d»as!");
		return false;
	}
	
	if (month == 2) { // check for february 29th
		var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
		if (day>29 || (day==29 && !isleap)) {
			alert("Febrero de " + year + " no tiene " + day + " dias!");
			return false;
		}
	}
	
	dateStr = month + "/" + day + "/" + year;
	return true;
}





function formatInput(dateStr){
	var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{4})$/;
	var matchArray = dateStr.match(datePat); 
	month = matchArray[3]; 
	day = matchArray[1];
	year = matchArray[4];
	return (month + "/" + day + "/" + year);
}





function dispDate(dateObj) {
	month = dateObj.getMonth()+1;
	month = (month < 10) ? "0" + month : month;
	day   = dateObj.getDate();
	day = (day < 10) ? "0" + day : day;
	year  = dateObj.getYear();
	if (year < 2000) year += 1900;
	return (day + "/" + month + "/" + year);
}



function ovulationCalc(pregform) {
	menstrual = new Date(); // creates new date objects
	ovulation = new Date();
	today = new Date();
	cycle = 0, luteal = 0; // sets variables to invalid state ==> 0


	if (isValidDate(pregform.menstrual.value)) { // Validates menstual date 
		menstrualinput = new Date(formatInput(pregform.menstrual.value));
		menstrual.setTime(menstrualinput.getTime())
	}
	else return false; // otherwise exits
		

	cycle = (pregform.cycle.value == "" ? 28 : pregform.cycle.value); // defaults to 28
	// validates cycle range, from 22 to 45
	if (pregform.cycle.value != "" && (pregform.cycle.value < 22 || pregform.cycle.value > 45)) {
		alert("Tu ciclo es demasiado corto o demasiado largo \n"
		+ "para que el cˆlcuo sea preciso! Igualmente intentaremos \n"
		+ "completar el cˆlculo con los valores ingresados. ");
	}

	luteal = (pregform.luteal.value == "" ? 14 : pregform.luteal.value); // defaults to 14

	// validates luteal range, from 9 to 16

	if (pregform.luteal.value != "" && (pregform.luteal.value < 9 || pregform.luteal.value > 16)) {
		alert("Tu fase lìtea es demasiada corta o demasiada larga \n"
		+ "para que el cˆlcuo sea preciso! Igualmente intentaremos \n"
		+ "completar el cˆlculo con los valores ingresados. ");
	}


	// sets ovulation date to menstrual date + cycle days - luteal days
	// the '*86400000' is necessary because date objects track time
	// in milliseconds;  86400000 milliseconds equals one day
	ovulation.setTime(menstrual.getTime() + (cycle*86400000) - (luteal*86400000));
	pregform.conception.value = dispDate(ovulation);

	// sets due date to ovulation date plus 269 days
	// sets fetal age to 14 + 266 (pregnancy time) - time left

	//return false; // form should never submit, returns false
	pregform.submit();

}


function pregnancyCalc(pregform) {


	menstrual = new Date(); // creates new date objects
	ovulation = new Date();
	duedate = new Date();
	today = new Date();
	cycle = 0, luteal = 0; // sets variables to invalid state ==> 0


	if (isValidDate(pregform.menstrual.value)) { // Validates menstual date 
		menstrualinput = new Date(formatInput(pregform.menstrual.value));
		menstrual.setTime(menstrualinput.getTime())
	}
	else return false; // otherwise exits



	cycle = (pregform.cycle.value == "" ? 28 : pregform.cycle.value); // defaults to 28

	// validates cycle range, from 22 to 45

	if (pregform.cycle.value != "" && (pregform.cycle.value < 22 || pregform.cycle.value > 45)) {
		alert("Tu ciclo es demasiado corto o demasiado largo \n"
		+ "para que el cölcuo sea preciso! Igualmente intentaremos \n"
		+ "completar el cölculo con los valores ingresados. ");
	}



	luteal = (pregform.luteal.value == "" ? 14 : pregform.luteal.value); // defaults to 14

	// validates luteal range, from 9 to 16

	if (pregform.luteal.value != "" && (pregform.luteal.value < 9 || pregform.luteal.value > 16)) {
		alert("Tu fase l“tea es demasiada corta o demasiada larga \n"
		+ "para que el cölcuo sea preciso! Igualmente intentaremos \n"
		+ "completar el cölculo con los valores ingresados. ");
	}


	// sets ovulation date to menstrual date + cycle days - luteal days
	// the '*86400000' is necessary because date objects track time
	// in milliseconds;  86400000 milliseconds equals one day

	ovulation.setTime(menstrual.getTime() + (cycle*86400000) - (luteal*86400000));
	pregform.conception.value = dispDate(ovulation);



	// sets due date to ovulation date plus 269 days
	duedate.setTime(ovulation.getTime() + 266*86400000);
	pregform.duedate.value = dispDate(duedate);


	// sets fetal age to 14 + 266 (pregnancy time) - time left
	var fetalage = 14 + 266 - ((duedate - today) / 86400000);
	weeks = parseInt(fetalage / 7); // sets weeks to whole number of weeks
	days = Math.floor(fetalage % 7); // sets days to the whole number remainder
	pregform.diasfeto.value = fetalage;
	// fetal age message, automatically includes 's' on week and day if necessary
	fetalage = weeks + " semana" + (weeks > 1 ? "s" : "") + " y " + days + " d&iacute;as";
	pregform.fetalage.value = fetalage;

	// return false; form should never submit, returns false
	pregform.submit();


}