We sometimes use past tenses to describe things in the present or future that are imagined or unreal. It's time we went. We are using It's time... here to say that something is not happening ...

Kylian Mbappé’s start at Real Madrid has been challenging since his free transfer from Paris Saint-Germain this past summer.

TA-form verbs indicate action in the past or the perfective aspect. That is what we did in the past or what we have done. And if we combine TA-form verbs and KOTO GA ARIMASU, we can talk about ...