I have a correspondence written by another human being making observations from that Wednesday, during which they lived and experienced things. Therefore we can be fairly certain the Earth existed on Thursday as well.
We cannot say the same for retroactive, presumed histories, the assumption of which constrains the possible effects that could generate the current-day results we measure.
The observer themselves placed their observations of the time and date as part of their larger observations of Wednesday's events.
The key here is the difference between an active observer intentionally communicating information forward from their present time and an observer looking into the past, attempting to infer events without any observer at that time to corroborate assumptions.
