One thing I am embarrassed to admit is I have never sat down and took the time to memorize the days of the month. It is something so easy to do but it is also just as easy to use numbers to communicate the days. It is so easy to confuse things when you aren’t using the correct names of the days.
With just a little bit of effort they are now memorized. I have also added them into a deck in Anki. The great thing about Anki is it is has a intelligent scheduler and will continue to reintroduce words to you over spaced intervals to ensure it is committed to memory.