Currently in concrete entry types, only Observation has a fixed attribute to record when an entry is made. We need similar attributes in Evaluation and other entry classes in the context of CDS.
Normally the timestamp of the Composition where the entries are included will be used, but when building CDS rules (using GDL) one does not want to go to the Composition level in order to figure out what is the latest evaluation or observation of a given archetype.
Using an archetype-specific element isn't a good solution because then this element will need to be added to all archetypes and the paths point to this element will be all different from archetype to archetype. It really is a generic requirement that should be dealt with on a RM level.