Is it possible to use an EFF in a case statement in OTBI?

Summary:

I am working on a report trying to calculate days between LOA End Date and the Estimated RTW Date (EFF) in the system. The case statement is producing an error, and I believe it is coming from the EFF since I have done this calculation before using delivered date fields. Any help is appreciated, thanks!

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

CASE WHEN "Assignment Event Details"."Effective End Date" = date '4712-12-31' THEN NULL