I just got Calendars working, they can work in combination with timers, see: http://blog.athico.com/2009/12/last-week-i-blogged-about-cron-and-int.html I'm just adding start/end support to the timer functionality too. Feedback welcome. Unit tests are here: http://fisheye.jboss.org/browse/JBossRules/trunk/drools-compiler/src/test... testNoProtocolIntervalTimer testIntervalTimer testCronTimer testCalendarNormalRuleSingleCalendar testCalendarNormalRuleMultipleCalendars testCalendarsWithCron testCalendarsWithIntervals Mark