You probably need latest tag reachable, not latest tag created:
git describe --tags --abbrev=0
Anyway, just in case you really need last tag created:
git does have two kinds of tags: lightweight and annotated. If your tags are lightweight then tough luck, you can't do this, creation date is not tracked. If you have access to filesystem where your remote repo is stored, then you can try checking timestamps on files in /refs/tags - but this info is not necessarily accurate (it's only timestamp of creation of tag file in this particular repo).
For annotated tags, however, you CAN obtain creation date; once you get sha (by ls-tree or other means), run:
git cat-file -p <sha>
to show tagger, message and creation date or simply:
git show <sha>
to additionally show referenced commit, too.
Using this information in script is doable (maybe not trivial due to date format).
I was going to refer you to git internals description about tags, but turns out, that all this info is also described on ProGit, Git Basics - Tagging.