I tried passing a value in RFC 2822 format to the DateTime and CDate functions respectively and on each occasion I get a "type mismatch" error. I subsequently re-formatted each of the values in "YYYY/MM/DD HH:MM:SS" format (which is an ugly hack) and they were succesfully cast to Date data types.

Now ... am I missing something really obvious here, or does Excel VBA really not support RFC 2822 Date format, which has been around in one form or another since 1980-something and is used by damn near everything on the internet???!!

I don't believe that, there must be a built-in that can cast an RFC 2822 date string to a Date data type.