code: public static DateTime toDateSimple(String str, TimeZone timeZone) throws PageException {
  	DateTime dt = toDateSimple(str, CONVERTING_TYPE_OFFSET, true, timeZone, null);
  	if (dt == null) throw new ExpressionException("can't cast [" + str + "] to date value");
  	return dt;
      }
docs: converts a Object to a DateTime Object, returns null if invalid string
  
  @param str String to Convert
  @param timeZone
  @return coverted Date Time Object
  @throws PageException