Biden came out and have a speech on election night that he was confident that he was gonna win so I assume they were confident by 12am to 3am or so. (Wisconsin dumped all their votes at 5am)
I have no idea about Trump but I think his Team was confident early on that he was going to win(seeing the strong margins in Florida, and his projected victories in Texas and the rest of the south and lower midwest(non Ga or NC) was going to get him reelected. I assume he was most confident from 7 30pm to 11pm most likely
I would assume by 2 or 3 in the morning, it seemed like that the time Biden was gonna pull through very barely but as the days went on, he won the election and later on the Senate(in January) making it a good year for the Democrats
I remember reading in some article that Biden's data team knew for certain the morning after
Election Day that he would win.