Ohhh.Well that makes sense now. I never really accounted for Curiosities of Lotus Asia or Bohemian Archive in Japanese Red so that's why my timeline is wrong. At least, it was wrong past Phantasmagoria of Flower View :x
But I'd still like another one of Aya's newspapers to completely confirm the dates...
Anyway, back on the topic of age, it's possible that even with time actually passing, nobody ages...?
I'd probably say Reimu, Marisa, Sakuya, and Sanae are pretty much the same age, but Sakuya seems older because... she has "lived longer" because she's been stopping time a lot?
Cirno is obviously over sixty years old (since she remembers the flower festival thing in PoFV) and Medicine is even younger since she (apparently) did not know of it and she's listed as a young youkai in Perfect Memento in Strict Sense anyway.
Akyu is over ten years old.
Remilia and Flandre are 500 and 495 years old, respectively (as we all know), while Chiyuri and Yumemi are 15 and 18 years old, respectively, when we last saw them.
Touhou Wiki says Kanako and Suwako are at least 2300 years old, Kaguya and Mokou are at least 1300 years old, and Yuyuko is at least 1000 years old.