Handling Invalid Dates in a CASE statement in OTBI

Summary:

How do you replace 00--0 with an actual date in OTBI? Getting error with CASE statement below

Content (required):

My CASE statement is coming back with an error when trying to replace invalid date 00--0 in my Effective Start Date column.

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):

CASE WHEN "Workforce Management - Worker Assignment Real Time"."Worker Assignment Details"."Effective Start Date" = '00--0' THEN "Worker"."Employee Hire Date" ELSE "Workforce Management - Worker Assignment Real Time"."Worker Assignment Details"."Effective Start Date", "Worker"."Employee Hire Date" END