The simplest explination I can think of...

[UnstoppableSound]

This is relating to the ever lasting question of the aging of Disney characters in the 10 year period of BbS-KH1, and why Cindarella, Snow White, etc. don't look any older in KH1.

Here it is...

Do you think it's possible that time passes differently in different worlds?

Think about it, maybe while in the main KH worlds (Destiny Islands, Radiant Garden, etc.) 10 years goes by, while in some worlds (The princesses worlds particularly) only 10 months or so go by.

In some worlds, the case might be different. We havn't seen much of Olympus Colliseum yet, but two possibilies are that:

If Hercules is a teenager like near the beginning of the film, then the time is either the same as DI, RG, or just slightly different (10 yrs in DI, RG=9/8 Years in OC).
-or-
If Herc is an adult, it could either be 10 years going by, or less.

For Deep Space (Lilo and Stitch world), these are the possibilities I'v come up with:

10 Years: In an episode of Lilo and Stitch the series, it was stated in the episode "Skip" that Stitch ages differently than other species, as Stitch still looked the same after 10 years had gone by. Stitch may age much slower than usual, but it's most likely that he's just completely ageless.
As for other characters in Stitch's world (Jumba, Pleakly, Gantu, if they where to appear), it was also shown in that same episode that they didn't really age that much after 10 years (They all looked pretty much the same).
As for Lilo, wherever her world is at this point, well, if Stitch ended up in her world emediatly after the events of BbS, then she would be her normal age in BbS, and in KH1/2 she would be a teenager. Or if Stitch didn't end up in Lilo's world until 10 years LATER, then she would be her normal age in KH1/2, where as in BbS, she is most likely not even born yet.

Or the same could apply as in the Princess worlds, and vice versa.

(I don't even know why I'm talking about Lilo, seeing as it's not very likely she'll appear)

So there you have it, I hope you guys find this easy to follow. I really wasn't expecting it to go on this long.

I read the first couple sentences (regarding time passing by differently in different worlds) and I have to agree. I mean, it's entirely possible seeing as how in universe (according to science...which I believe is bull shit, but we have to base our comparison on something here) time passes differently on each planet relative to how close or far away they are from the Sun. If you think of the KH universe in a similar fashion, then this concept could easily apply. Therefore, it could easily be a possibility.