Punctuation before or after superscript of date?

You wouldn’t write it out as “twenty fif.th”, so you wouldn’t put the period in the middle of the word when using superscripts either.

If you are using a style guide, check to see if dates should have superscripts or not. APA style, for example, says to make it regular case, which would be:

• on the 25th.

If you’re not using a style guide, consider writing it like this.

I think it's more of a stenography/typewriting question. If you are writing it then you put it in the natural place. If you are typesetting it with a computer, you can kern it. See below the period is kerned by -0.8 em.