Whenever you travel through time the DeLorean updates the time circuits to reflect the current date and time. How does it know the current date and time of its arrived destination?

I guess what I am asking is, when the lighting stuck the delorean and jumped it back to 1885. Did the time circuits *know* it was 1885, or did it not know, because it wasn't entered.

![enter image description here](https://i.stack.imgur.com/ouSerl.png)