How can I format my external APFS disk?

I formatted my external backup disk as APFS pretty easily recently. Just used the Disk Utility as per normal.  But I discovered very quickly that while Time Machine could read from APFS it could not write to it.  Maybe in the future but not now - 10/15/17 - not. So I thought to reformat it … Continue reading How can I format my external APFS disk?