The "" in a formula is seen as text and the formula will be looking for a date. I always do ISNULL(Rehire_Date) instead of trying to do Rehire_Date=<something that means blank date>.

The ISNULL doesn't work from what I can tell when when using within Timberline.  I know that would work if I was using a formula in Crystal but I get an error in the formula when trying to save within the Sage formulas.

Try using zero instead of blank

That appeared to do  the trick. Thanks!

You are right, ISNULL is not a function available in Sage formulas. So, the workaround is IF(Year(Rehire Date)<0, Hire Date, Rehire Date). I checked and this works. Zero also works. But, I don't know which will return the correct date for you. You'll need to test. :-)