There are three tags with a very similar meaning:
They should be probably merged.
And possibly more.
I dislike tags that are this specific to the API level, and the questions in the dateformat tag, while probably referring to one of the two APIs above, still are about formatting dates.
I'd be cautious about doing anything with the dateformat tag; there are other date-format-specific tags in the system, and while I'm not eager to get rid of them, there could be people that are searching on visual-basic and dateformat or java and dateformat. However, I still approve of merging the dateformat tag into the date-formatting tag.
We'll do a merge of all the tags if there's no major objections.