Here are some more Birthdays to keep the discussion rolling
Roxas’ birthday- 12/22
KH2’s release in Japan- 12/22
Xion’s birthday- 5/20
Kh Day’s release in Japan- 5/20
Axel’s birthday- 12/7, 9/29 or 3/26* he first appeared in com but he’s more important in Days and kh2 (since March 28th is already used for the birthday of the entire series and sora i used kh2’s release year in the US to determine the last date also the last date can’t be used for Axel if Isa also uses it)
Isa’s birthday- 3/26, 7/11 or 11/17 Isa first appeared in kh2 but his younger appearance showed up in bbs and that’s why the last two dates are scrambled up versions of the Japanese release date of that game
Hayner’s birthday- 9/2 kh2’s release in the EU without the extra nine
Olette’s birthday- 9/28 kh2’s release in Australia
Pence’s birthday-2/12,12/2,1/22 or 3/29 a jumbled up version of kh2’s Japanese release or the original release of Kh2 final mix
Xehanort/Ansem SOD/Xemnas and maybe Terranort- 7/22 the release of dark road
Luxu- the same date as the release of the update where we see him for the first time in Japan (hard to find exact dates for Chi game updates)
unpossessed Braig- the same date as the release of the update where we see Luxu for the first time in the US
Dilan/Xaldin- 9/26, 3/9 or 3/2 the first date references the release of kh2 in EU with the day replaced by the year the last two dates uses his org rank for the month and takes a number away from the day kh2 released in the EU for the day
Even/Vexen- 5/6, 4/5, 4/25 or 4/6 the first date comes from the release of com in the EU as he first appeared in com the second date moves the month of com’s release in the EU to the day and uses the empty month slot to put his org rank, the third takes the second date but replaces using the month of com’s release in the EU with using com’s release year in the EU for the day and the final one just replaces the month of com’s release in the EU with his org rank
Aeleus/Lexaeus- 1/13, 5/13, 5/31 or 3/15 the first date is com’s release in Australia the second takes the first and replaces the month with his org rank and the last two take the second one and mixes it up
Ienzo/ Zexion- 3/27, 7/23, 6/29, 6/27, 6/7 or 3/6 the first date references the Japanese release of RE:com. The second date scrambles up the first. The third date uses his org rank for the month and the day of the Japanese release of RE:com. The fourth date takes the first date and replaces the month with his org rank. The fifth references the first date and gets rid of the unnecessary 3 and 2 and the final date takes the first date and replaces the day with his org rank.
Demyx- 10/9, 9/10, 9/23, 2/25 or 1/23 the first two dates reference the EU/Australian release date of kh days. The second date scrambles up the release of kh2 final mix. the third references the XBOX release of kh3 remind and scrambles the Japanese release of kh2 and the final one references the PS4 release of kh3 remind
Luxord- 12/10, 10/12, 5/27, 5/3, 5/10, 10/5, 10/27, 10/23 the first two reference both the Japanese release of kh2 and his org rank. The next two dates reference kh days‘ release in Japan. The fifth date takes the last twos dates and replaces the day with his org rank. Then the sixth date scrambles the fifth. The seventh date takes the third and replaces the month with his org rank and the final date references kh3 reminds release on PS4 and his org rank.