we can reproduce it by following steps.
1. create a knowledge session. and call the method 'fireAllRules()'
2. reload knowledge session.
3. crate and build a timer rule.
4. fire the timer rule.
[Actual Result]
the timer rule cannot work fine.

[Expected Result]
the timer rule can work fine.

(please check the attachement 'TimerAndCalendarTest.java.txt')