code: public static DateTime toDateSimple(String str, short convertingType, boolean alsoMonthString, TimeZone timeZone, DateTime defaultValue) {
  	str = StringUtil.trim(str, "");
  	DateString ds = new DateString(str);
  
  	// Timestamp
  	if (ds.isCurrent('{') && ds.isLast('}')) {
  	    return _toDateSimpleTS(ds, timeZone, defaultValue);
  	}
  	DateTime res = parseDateTime(str, ds, convertingType, alsoMonthString, timeZone, defaultValue);
  	if (res == defaultValue && Decision.isNumber(str)) {
  	    return numberToDate(timeZone, Caster.toDoubleValue(str, Double.NaN), convertingType, defaultValue);
  	}
  	return res;
      }
docs: converts the given string to a date following simple and fast parsing rules (no international
  formats)
  
  @param str
  @param convertingType one of the following values: - CONVERTING_TYPE_NONE: number are not
  converted at all - CONVERTING_TYPE_YEAR: integers are handled as years -
  CONVERTING_TYPE_OFFSET: numbers are handled as offset from 1899-12-30 00:00:00 UTC
  @param alsoMonthString allow that the month is defined as english word (jan,janauary ...)
  @param timeZone
  @param defaultValue
  @return