Editing Permalinks when Creating Pages

WP does not allow creating Permalinks ending with (domain)...-24.12.2012?

[deeper]

Hi,
on one of my older sites which I like to redesign now with WP, I created pages with URLs which reflect the date of events by ending with the date of this event.

Let's say the URL of a page on the old static site is ...(domain)/holy-party-24.12.2012.html
Redesigning it in WP - all permalinks are manually edited, because permalink settings are not very helpful - WP automatically changes the slug
holy-party-24.12.2012 into
holy-party-24-12-2012.

You can type both URLs in your browser and both work (any kind of automatical URL-redirection I guess). But I need the "real" URL "...24.12.2012".

If such slugs were against any URL-rules and WP therfore does a good job, why was it possible to create it on a static site?

Is there a proper way to convince WP accepting slugs ending with "-24.12.2012"?

Thanks for help.

[lucy24]

I suppose it's too late to try to convince you that filenames containing literal periods are a dreadful idea? The same applies to many, many things in this life that are technically legal. It means, for example, that you can't make simple rules involving

/[^./]+\.html

but instead have to go all complicated.

[deeper]

I like simple things and you may remember my need to change .html-URLs into "without".

This site only has four pages with date-URLs like above and they get almost no backlinks at all. There are further sites, just a few and it will be a similar situation there.

Hm, may be I should delete them and re-create with different URLs, but it sounds like choosing "pest or cholera".