How do I know when I'm done with a level?

[PeachVsEggplant]

For example, 1980 and 1985 I found the hidden cats outside the arcade, found all cats inside, all hidden cats inside, the coin, completed the arcade game and got the battery... but when I go back to the screen to choose another year it doesn't display a "time" above the year so something makes me feel like I haven't "finished" the level. Theres nothing from the 2 cats confirming I've found everything and to move on?

[Marie (ㅇㅅㅇ❀)]

the time is for when you click on the little stop watch above the level and it records your time for how long it takes you to complete the level

[GalPsuche]

I have this happening with the year 3000 BC too. I don't have a fix but I'm in the same boat.