I've removed almost all of the time and date functions from the Language*.php files of my working copy (now checked in as the localisation-work branch), replacing them by format strings in the style of PHP's date() function. They're much easier to understand than PHP code, so hopefully this will encourage people to review and edit them.
There is a chance that I made a transcription error during this process, and there is also the chance that the original language files had an incorrect or non-ideal date format to start with. So I invite everyone to have a look at them. I formatted the date "15 January 2001, 12:34" in every defined date format in every language, and put all the resulting strings at:
http://www.mediawiki.org/wiki/Date_formats
One deliberate difference since the previous version of MediaWiki is to make our ISO 8601 formats technically correct. This format had been labelled "ISO 8601" since I introduced it to the wikitext date formatter, but somehow when it was copied to the language files, and a time format added, someone forgot to include the "T" separator between time and date. The ISO 8601 format was originally requested by Ray Saintonge in the interests of standardisation, and I would like to see MediaWiki remain true to that goal.
You can find the format strings themselves in the Messages*.php files at:
http://svn.wikimedia.org/viewvc/mediawiki/branches/localisation-work/phase3/...
In other news, I think the localisation-work branch is now ready for beta testing.
-- Tim Starling