I just had to write the following email:
Yo, looks like we need to reschedule again. I am not Jewish and thus lack awareness of most Jewish holidays. [Boss] is Jewish and will be out of here early tomorrow.
Sorry bout that – totally my WASPy fault.
The sad thing is as former Religion minor and Half-Jew, I should know these things.
I know - you're impressed with both my smarts and my professionalism.