Not without a hack: replace org.drools.core.util.DateUtils by the modified code given below. Specify drools.dateformat as a list of date formats separated by a newline, e.g.: System.setProperty( "drools.dateformat", "dd-MMM-yyyy HH:mm\ndd-MMM-yyyy" ); Make sure that a more comprehensive format is first, they are tried in the given order, and a longer String is accepted for a shorter format. The very first format is used for printing (whenever Drools feels like doing so). On error, you may see a message such as Invalid date input format: [1-5-1985] it should follow one of: [dd-MMM-yyyy HH:mm] or [dd-MMM-yyyy] And the default format is dd-MMM-yyyy - NOT dd-mmm-yyyy as "Expert" would have it. -W package org.drools.core.util; import java.text.DateFormat; import java.text.DateFormatSymbols; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Locale; import org.drools.type.DateFormats; public class DateUtils { private static final long serialVersionUID = 510l; private static final String DEFAULT_FORMAT_MASK = "dd-MMM-yyyy"; private static final String DATE_FORMAT_MASK = getDateFormatMask(); private static final String DEFAULT_COUNTRY = Locale.getDefault() .getCountry(); private static final String DEFINE_COUNTRY = getDefaultContry(); private static final String DEFAULT_LANGUAGE = Locale.getDefault() .getLanguage(); private static final String DEFINE_LANGUAGE = getDefaultLanguage(); private static ThreadLocal<SimpleDateFormat[]> df = new ThreadLocal<SimpleDateFormat[]>() { protected SimpleDateFormat[] initialValue() { DateFormatSymbols dateSymbol = new DateFormatSymbols(new Locale( DEFINE_LANGUAGE, DEFINE_COUNTRY)); String[] masks = getDateFormatMask().split( "\\n" ); SimpleDateFormat[] dateFormats = new SimpleDateFormat[masks.length]; for( int i = 0; i < masks.length; i++ ){ dateFormats[i] = new SimpleDateFormat(masks[i], dateSymbol); } return dateFormats; }; }; private static String getDefaultLanguage() { String fmt = System.getProperty("drools.defaultlanguage"); if (fmt == null) { fmt = DEFAULT_LANGUAGE; } return fmt; } private static String getDefaultContry() { String fmt = System.getProperty("drools.defaultcountry"); if (fmt == null) { fmt = DEFAULT_COUNTRY; } return fmt; } /** Use the simple date formatter to read the date from a string */ public static Date parseDate(final String input, DateFormats dateFormats) { for( SimpleDateFormat dateFormat: df.get() ){ try { Date date = dateFormat.parse( input ); return date; } catch (final ParseException e) { } } String valids = DATE_FORMAT_MASK.replace( "\n", "] or [" ); throw new IllegalArgumentException("Invalid date input format: [" + input + "] it should follow one of: [" + valids + "]"); } /** Use the simple date formatter to convert the Date into a String */ public static String format(final Date input) { return df.get()[0].format( input ); } /** Converts the right hand side date as appropriate */ public static Date getRightDate(final Object object2, DateFormats dateFormats) { if (object2 == null) { return null; } if (object2 instanceof String) { return parseDate((String) object2, dateFormats); } else if (object2 instanceof Date) { return (Date) object2; } else { throw new IllegalArgumentException("Unable to convert " + object2.getClass() + " to a Date."); } } /** Check for the system property override, if it exists */ public static String getDateFormatMask() { String fmt = System.getProperty("drools.dateformat"); if (fmt == null) { fmt = DEFAULT_FORMAT_MASK; } return fmt; } } On 31/01/2013, richie <haoruiqian(a)gmail.com&gt; wrote: