function isEmpty(inputStr) {
        if (inputStr == "" || inputStr == null) {
                return true
        }
        return false
}

function isNumber(inputStr) {
        for (var i = 0; i < inputStr.length; i++) {
                var oneChar = inputStr.charAt(i)
                if (oneChar < "0" || oneChar > "9") {
                        return false
                }
        }
        return true
}

function inRangeDay(inputStr) {
        num = parseInt(inputStr)
        if (num < 1 || num > 31) {
                return false
        }
        return true
}

function inRangeYear(inputStr) {
        num = parseInt(inputStr)
        if (num < 1900 || num > 3000) {
                return false
        }
        return true
}

function isValidDay(inputStr) {
        if (isEmpty(inputStr)) {
                alert("Por favor introduzca el día antes de presionar calcular.")
                return false
        } else {
                if (!isNumber(inputStr)) {
                        alert("Por favor asegurese que introdujo un número de día valido.")
                        return false
                } else {
                        if (!inRangeDay(inputStr)) {
                                alert("Por favor introduzca un día valido.")
                                return false
                        }
                }
        }
        return true
}

function isValidYear(inputStr) {
        if (isEmpty(inputStr)) {
                alert("Por favor introduzca el año antes de presionar calcular.")
                return false
        } else {
                if (!isNumber(inputStr)) {
                        alert("Por favor asegurese que introdujo un número de año valido.")
                        return false
                } else {
                        if (!inRangeYear(inputStr)) {
                                alert("Por favor introduzca un año valido.")
                                return false
                        }
                }
        }
        return true
}
function makeArray(n) {
        this.length = n
        for (var i=1; i <= n; i++)
                this[i] = null
                return this
}
var maxday = new makeArray(12)
maxday[1] = 31
maxday[2] = 28
maxday[3] = 31
maxday[4] = 30
maxday[5] = 31
maxday[6] = 30
maxday[7] = 31
maxday[8] = 31
maxday[9] = 30
maxday[10] = 31
maxday[11] = 30
maxday[12] = 31
var monthname = new makeArray(12)
monthname[1] = "Enero"
monthname[2] = "Febrero"
monthname[3] = "Marzo"
monthname[4] = "Abril"
monthname[5] = "Mayo"
monthname[6] = "Junio"
monthname[7] = "Julio"
monthname[8] = "Agosto"
monthname[9] = "Septiembre"
monthname[10] = "Octubre"
monthname[11] = "Noviembre"
monthname[12] = "Diciembre"
var adddays = new makeArray(7)
adddays[1] = 14
adddays[2] = 35
adddays[3] = 70
adddays[4] = 84
adddays[5] = 161
adddays[6] = 189
adddays[7] = 280

function calcNewDate(month,day,year,adddays) {

        newday = eval(day) + adddays

        newmonth = month + 1

        newyear = eval(year)
 
         var max

        for (var i = 0; i < 12; i++) {

          if (newmonth == 2 && (newyear % 4) == 0) {
	          max = 29

          } else

            max = maxday[newmonth]
          if (newday > max) {
            newday = newday - max

           newmonth = newmonth + 1

            if (newmonth > 12) {

              newyear = newyear + 1

              newmonth = 1

            }

          }

         else

            break

        }

        var datestring = monthname[newmonth] + " " + newday + ", " + newyear

        return datestring

}


function calc(form) {

        day = form.day.value

        year = form.year.value

        monthnum = form.month.selectedIndex
   	
   	 if (isValidDay(day)) {

          if (isValidYear(year)){

            form.conception.value = calcNewDate(monthnum,day,year,adddays[1])

            form.beginrisk.value = calcNewDate(monthnum,day,year,adddays[2])

            form.endrisk.value = calcNewDate(monthnum,day,year,adddays[3])
 
            form.beginorgan.value = calcNewDate(monthnum,day,year,adddays[2])
 
            form.endorgan.value = calcNewDate(monthnum,day,year,adddays[3])

            form.endfirst.value = calcNewDate(monthnum,day,year,adddays[4])

            form.preemies.value = calcNewDate(monthnum,day,year,adddays[5])

            form.endsecond.value = calcNewDate(monthnum,day,year,adddays[6])

            form.duedate.value = calcNewDate(monthnum,day,year,adddays[7])
          }
        } 
}