I have done a quick test of the Challenge management section to see ih the awkward mess of the dates selection has improved (see older poorly answered messages in this forum).

At least today it is working, even for countries outside the US. But still this feature does not accept that a challenge starts the same day, even with accepting late entries, although team users contributions are tallied only a few minutes before midnight UTC.

Well, why not, but then today's date should not be selectable, and the error message should not show a wrong format to use (US of course!).