It seems when we have a LHS like this:
Order( $current.time after[1m] time )

Drools will fail in the evaluation with this exception:
Caused by: java.lang.ClassCastException: java.util.Date cannot be cast to java.lang.Long
at org.drools.core.base.extractors.ConstantValueReader.getLongValue(ConstantValueReader.java:48) [drools-core-6.1.0.Final.jar:6.1.0.Final]
at org.drools.core.base.evaluators.AfterEvaluatorDefinition$AfterEvaluator.evaluate(AfterEvaluatorDefinition.java:365) [drools-core-6.1.0.Final.jar:6.1.0.Final]

This is a PR that demonstrates the issue
https://github.com/droolsjbpm/drools/pull/554