Version 5.0 of The Battle Cats released in Japan on April 1, 2016, and internationally on April 22, 2016.

Quick scoop

That update is often remembered as a major foundation update, because it added new units, many True Forms, and the Catseye feature.

Dates at a glance

Region| Release date
---|---
Japan| April 1, 2016 11
International| April 22, 2016 11

Context

A later retrospective video also described Version 5.0 as “the Foundation of the Future,” underscoring how important that update was for the game’s long- term progression.

TL;DR: Battle Cats Version 5.0 came out in April 2016 — April 1 in Japan and April 22 internationally.