This is consistent with the way we show the duration of a budget and its
phases. Since budgets are the section with the most recent changes in
the admin area, we're using it as a reference.
Note that, unlike budgets (which are shown to finish at the beginning of
their ending day), a poll has always been considered to finish at the
end of their ending day, so we're showing it this way.
We're also solving a minor usability issue. While it's pretty intuitive
that a poll starting on a certain date will start at the beginning of
the day, a poll ending on a certain date isn't clear about when it
finishes exactly: is it at the beginning of the day, or at the end of
the day?
So now we're making this point clear.
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