Except Biff didn't even tell Marty what time of day it happened. Besides I am pretty sure the exact time of day is on the time circuits too.
"1-800 Spank me? I know that number." Scott Calvin, The Santa Clause.

Maybe but remember Doc says "the specific circumstances of how where and when young Biff got his hands on the almanac"
The date is only one piece of info they need.

I'd like to think Doc also at some point thought something was up when he read the time display "where you were" readout that said Nov 12, 1955.
That is not the case or else they would have just gone there without confronting Biff.
"1-800 Spank me? I know that number." Scott Calvin, The Santa Clause.

I'd like to think Doc also at some point thought something was up when he read the time display "where you were" readout that said Nov 12, 1955.

Yep. Then Doc would have to rebuild his time machine and then they'd be able to save 1985. I guess it was pretty hard to miss that 1985 was under Biff's reign after a while.
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I think what tipped Doc off to there being something wrong was when he got to his lab and saw it "an awful, awful, awful, awful mess". While Marty was knocked out, he probably did some snooping around, including going to the library as he said. Then he saw the story about George being murdered and went to the cemetary to wait for Marty to arrive, as he figured he would.