31 Oct 2020 - Blue Moon

• While 2020 featured a rare Halloween “blue moon ”
  — the second of two full moons during the same calendar month
  — the blue moon that will be appearing in 2021 is a different type of blue moon. The Aug. 22, 2021 full moon will be considered a seasonal blue moon,
  which is the third of four full moons appearing during the same season.
  so; 31 oct 2020 - was a full moon & A BLUE MOON too
  and; a seasonal blue moon is not really a blue moon
  - a blue moon is 2 full moons in one calendar month
  so, 22 aug 2021 is a full moon, but, NOT a blue moon