For 2, 3, 22, 23, read the second part: https://drhagen.com/blog/the-missing-23rd-of-the-month/ https://drhagen.com/blog/the-missing-23rd-of-the-month/. (short

For 2, 3, 22, 23, read the second part: https://drhagen.com/blog/the-missing-23rd-of-the-month/ https://drhagen.com/blog/the-missing-23rd-of-the-month/. (short version: people used to sometimes write 2d, 3d, 22d, 23d.). This also explains why 12 and 13 don't show the deficit.