2699516 - Unable to use $session.system_date with calculated field and function DATS_DAYS_BETWEEN

User is working with Custom CDS view and attempting to use function DATS_DAYS_BETWEEN in a calculated field with session date  $session.system_date.  The variable is causing error:

Function DATS_DAYS_BETWEEN: At position 1, only Expressions, Literals, Columns, Paths, Parameters allowed

SAP S/4HANA Cloud Public Edition 1808

1. Create Custom CDS View
2. Create calculated field
3. Use Function

   DATS_DAYS_BETWEEN($session.system_date,$session.system_date)

4. Observe Error Function DATS_DAYS_BETWEEN: At position 1, only Expressions, Literals, Columns, Paths, Parameters allowed

Session variable $session.system_date is not valid type for function DATS_DAYS_BETWEEN.

Cast $session.system_date to proper type for function DATS_DAYS_BETWEEN

DATS_DAYS_BETWEEN(cast( $session.system_date as ABAP.DATS ), cast( $session.system_date as ABAP.DATS ))

DATS_DAYS_BETWEEN $session.system_date system_date , KBA , BC-SRV-APS-GKE , Generic CDS Key User Editor , Problem