docs: def wholeday(date: datetime.date) -> "Interval":
          """
          Returns an :class:`Interval` covering the date given (midnight at the
          start of that day to midnight at the start of the next day).
          """
          start = datetime.datetime.combine(date, datetime.time())
          return Interval(
              start,
              start + datetime.timedelta(days=1)
          )