>>35574964There's also some others not based on names like this.
1/10 is Flareon Day based on its nickname "the only king" (唯一王)
2/5 is Pikachu Day because its Dex number is 25
2/6 is Raichu Day because its Dex number is 26.
2/6 is Mewtwo Day because that's its birthday according to the journal in RBY
2/9 is Absol Day because its Sinnoh Dex number is 209.
3/12 is Minun Day because its Dex number is 312.
5/7 is Zorua Day because its Dex number is 570.
6/18 is Leafeon Day because its Dex number is 169 and that's the 169th day of the year.
7/5 is Mew Day because that's when it was discovered according to the journal in RBY.
7/7 is Jirachi Day because that's Tanabata.
11/1 is Ampharos Day because that's the Japanese Lighthouse Anniversary Day
2/7 is Umbreon Day, 4/17 is Tepig Day, 5/8-/59 is Growlithe+Arcanine Day, and 8/9 is Typhlosion Day, but I'm not totally sure why for those ones.