function isDate(dateStr) {
    var datePat = /^(\d{1,2})(\/|.)(\d{1,2})(\/|.)(\d{4})$/;
    var matchArray = dateStr.match(datePat); // is the format ok?

    if (matchArray == null) {
        //alert("Please enter date as either mm/dd/yyyy or mm.dd.yyyy.");
        return false;
    }

    day = matchArray[1]; // parse date into variables
    month = matchArray[3];
    year = matchArray[5];

    if (day < 1 || day > 31) {
        //alert("Day must be between 1 and 31.");
        return false;
    }

    if ((month==4 || month==6 || month==9 || month==11) && day==31) {
        //alert("Month "+month+" doesn't have 31 days!")
        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("February " + year + " doesn't have " + day + " days!");
            return false;
        }
    }

    if (month < 1 || month > 12) { // check month range
        //alert("Month must be between 1 and 12.");
        return false;
    }

    return true; // date is valid
}

function isNumeric(InString)
{
   //RefString = "-1234567890.,";
   // Pro nase potreby jen prirozena cisla
   RefString = "1234567890";
   DecimalPoints = 0;
   
   if (InString.length == 0)
    return (false);	

   for (i=0; i < InString.length; i++)
   {
      TempChar = InString.substring ( i, i+1 );

      if ( TempChar == "." ) { DecimalPoints++; } /* Can only have zero or one decimal points in a number */
      if (( TempChar == "-" ) && ( i != 0 )) { return ( false ); } /* Minus Sign must be first character */

      /* Check if current character is valid */

      if ( RefString.indexOf (TempChar,0) == -1)
      {
         /* character not found in RefString */
         return (false);
      }
   }
   if ( DecimalPoints > 1 )
      return ( false );

   return(true);
}







function isEmailAddress(EmailAddress)
{
  var mail=/^.+@.+\..{2,4}$/ 
  return (mail.test(EmailAddress));
}




function EmailZpravodajValid(formular)
{
if (!isEmailAddress(formular.user_email.value))
 {
  window.alert('Zadejte správně email!');
  formular.user_email.focus();
  return false;
 }
else
  return true;
}



function dotazValid(formular) {

 var x = formular.user_email.value;
 x = x.replace(/ /g,''); // nahrada (zde jen odstraneni) mezery
 
 var y = formular.message.value;
 y = y.replace(/ /g,''); // nahrada (zde jen odstraneni) mezery
 
 if (x=='') {
    window.alert('Zadejte Email!');
    formular.user_email.focus();
    return false;
 } else if (!isEmailAddress(formular.user_email.value)) {
    window.alert('Zadejte správně email!');
    formular.user_email.focus();
    return false;
 } else if (formular.trytry.value=='') {
    window.alert('Zadejte správný výsledek!');
    formular.trytry.focus();
    return false;
 } else if (y=='') {
    window.alert('Napište váš dotaz!');
    formular.message.focus();
    return false;
 } else return window.confirm('Opravdu odeslat?');
 
}





function zobrazURL(URL, sirka, vyska, zleva, shora) 
{
  window.open(URL, '', 'width=' + sirka + ', height=' + vyska + ', left=' + zleva + ', screenX=' + zleva + ', top=' + shora + ', screenY=' + shora + ', scrollbars=yes, resizable=yes');
}