code: def most_recent_year():
      
      aoc_now = datetime.datetime.now(tz=AOC_TZ)
      year = aoc_now.year
      if aoc_now.month < 12:
          year -= 1
      if year < 2015:
          raise AocdError("Time travel not supported yet")
      return year
docs: This year, if it's December.
      The most recent year, otherwise.
      Note: Advent of Code started in 2015