So I remember you getting that ask about the formation of Crystal Tokyo and how/when it came to be. I think I found an actually solid answer to how Crystal Tokyo came to be (at least in terms of the manga).
Sailor Cosmos mentioned to the Amazoness Quartet senshi that Usagi and the others would safely be reborn in the 30th Century through the “lambda power.” I’m assuming this is because the battle with Shadow Galactica and Chaos resulted in the people of the universe being destroyed. And due to Usagi’s sacrifice in the Galaxy Cauldron, she was able to bring about the power to restore everything.
So imagine that due to the nature of the battle, resulting in everyone’s “deaths,” the universe took a one-thousand year period to restore itself. This explains why Sailor Cosmos would say they would be reborn in the “30th Century” instead of their own time. The entire world was just thrust 1,000 years forward due to the lambda power within the cauldron. Once the 30th Century came, Usagi was able to go on with her life, and upon reaching age 22, assumed the throne after making her identity and powers known once the war with Chaos was over.
It also explains, vaguely, why in the final pages of the manga, we were able to assume that Usagi had just been impregnated (I mean, come one! She SAID that a new sailor soldier would be born soon!!!!). So This could be the reason the formation of Crystal Tokyo took place in the 30th Century and how to Earth was “in a stand-still” for one-thousand years.
~submitted by lepetitmeow
This is a great theory! I like it a lot! Thanks for sharing. ~Silvermoon424