i dont know what happend at your house last night,, how can scientist know what happend 1 million years ago
Ok so maybe I am wording my question of what you think accuracy is, no problem.
What time did you wake up today?
Do you have an alarm, if so what moment was it set for?
Do you deem that an accurate look into time?
Because if you do, I would be able to dispute it, what second what that alarm set? When did you consiously wake up? What moment did you stand out of bed? When did you fist open your eyes.
And if you can get the exact second, what is the millisecond? If you can figure that out we can continue to move down to smaller and smaller increments in time so that you never have the actual time.
Now lets say you have to the second the time you 'woke'
So that is 1 second range in 1 day. So that means 1 divided by 86,400 (seconds in a day) so that is : .00011.
If you put that out 20 billion years it is a range of: 2.2 million years. So there is accuracy in these models, but the range seems so big due to the enormous span of time we are discussing.