Does Atmos support chronological and event based retention?

Atmos has the ability to create policies in the management interface that allows for retention to be set on objects at various granular levels.  One of the ways that retention can be applied to objects is by metadata update which can certainly be considered event-based.  A metadata value can be updated programmatically which can trigger a retention policy to be applied.

Retention can also be applied based on system metadata such as create time, etc.  This can be considered chronological.

Am I interpreting your question correctly?