I mainly use mp3tag for processing BBC podcasts. These typically have filenames of form
where 'prg' is a truncated version of the original radio programme's name, and the 'yyyymmdd' portion is the original radio programme's transmission date.
I've developed several quite complicated action lists where I typically copy the filename to other fields (eg 'Album' or 'Title') then manipulate the filename and whatever was originally in those fields, using a series of regex based replaces, to reset them to values I want.
Unfortunately for some BBC programmes the same 'prg' letters are used to represent programmes transmitted several times per week, in somewhat differing formats. For example in one program what's transmitted on a Sat/Sun reports on a particular problem, while in the following Wednesday's transmission there's a phone-in about a related matter.
At the moment I end up with both sorts of programme in the same 'Album' subfolder on my mp3 player because I cannot distinguish between the two types of podcast which both have the same 'prg' value in their filenames.
I'd like to be able to derive the transmission date's day name from the yyyymmdd value in the filename. If you could provde a function which, when given 'yyyymmdd' returned an integer in range 1-7 or 0-6 or whatever, this would be extremely useful.