If this thread's title doesn't specify it's spoilery, don't bring any up.
Date article titles are now in the form 1 January
As there were no objections at forum:cardinal numbers, and it is now 1 October UTC, the bot is changing over to cardinal numbers, but leaving behind ordinal redirects.
This means that date articles are titled in the format 1 January, but you still have the option of linking to 1st January. The retention of redirects means that there is no need to change much of anything on the site.
Please do not delete ordinal redirects, though, as this will truly screw up the site.
This change has very little impact upon what you must use when linking dates in articles. In general, you should try to use the format seen in-narrative. That is, if a particular book uses the format 1 January, you should consider using that format. But if there is no narrative context — for instance, if you're giving a real world person's birthday — you can use whichever feels most natural to you.
You should, however, keep the date format the same within the same article.