Sorting mail by Date

[Taed Nelson]

I used to keep separate "record" and "mbox" files using ucb mail.  I would
  now like to merge them into one file sorted by date.

I was thinking that I could do something funky with sort-paragraphs while
  in some funky emacs ucb-mail-mode, but I don't know of any mail mode that
  doesn't require you to switch to RMAIL.  That would be a solution, but
  despite my love for Emacs, I hate Rmail.

It seems that someone else sometime would have wished to do this.

Anyone have a clue as to where I should start other than writing my own
  parser for a mail file?