If you have this set to evaluate as a conditional formatting argument it will not do what you think it will do.
What you probably want is to define a field as a calculation date type and set the calculation to your formula.
Then it should behave as prescribed.
Conditional formatting affects how data is presented on the layout.
Thanks, that was it, I thought Conditional Format would do it. Thanks I appreciate your time.
If using a fairly recent version of FileMaker, you could use Hide Object When to do what you want, but you'd need a different expression.
As an example, you could put layout text on your layout such as "Open", then set up:
so that this text is hidden when the field is not empty.
Could then be used with "Closed" text to hide this text when the above expression is True.
This is not necessarily a better way, just showing an alternative method.
In older versions of FileMaker, we'd use conditional formatting to hide/reveal such layout text by either changing the color to match the background or sizing the text extremely large to make it invisible. That may be what had you thinking in terms of a conditional format.