542,000,000 B.C.

In the real world

 * The Precambrian eon is coming to an end, and the Cambrian explosion is beginning to take place, during which most major animal phyla appear.

In the Kaiju Multiverse

 * A species of crustacean that lived in colonies on the ocean floor exists at around this time. In approximately 542 million years, one of these colonies would become Destoroyah.