Watchfile (and version numbers) for a braindead scheme

[debian-devel@liska.ath.cx (Olе Streicher)]

Hi,

I want to write a watch file for the "esomidas" package, which has
download URLs like

ftp://ftp.eso.org/pub/midaspub/13SEP/sources/13SEPpl1.1.tar.gz

(12 is the two-digit year, FEB the month of the release). I have some
problems with it: 

1. What should the version number look like for Debian? 13.09.1.1?

2. How do I convert these Month names into a number?

3. How can I access the subdirectory and search there for the same name?

Upstream will not change name or directory structure at all, since the
structure is such since 15 years.

Best regards

Ole