Day trip from Berlin to Wittenberg

Must be very well doable, years ago driven from Wittenberg to Berlin, it is not that far. With the train must be easy too as the station is not so far from the centre, which is very compact so very walkable. Can’t say much about the crowds depends most if there will be a festivity or not. During my visit in 2010 there where tourists but not too many, founded a pleasant lovely place. https://lutherstadt-wittenberg.de/en/

There are many day trip options. During a weekday, you can use a Brandenburg-Berlin Day ticket for 29 EUR for 2. The earliest train you could use it on is the 10:30 Regional Express that gets to Wittenberg Lutherstadt at 11:48. You must use regional train only for this ticket. Returns are at 18:12 20:12, and 22:25, all taking about an hour and 15 minutes or so.

To leave earlier, you can get a Regio 120 Ticket + Luther at 8:31 and take one of the evening return train with a Brandenburg-Berlin Night ticket for 62 EUR for 2.

All these require using only regional trains, there are no reservations, but since they originate and terminate at Berlin Hbf and Wittenberg Lutherstadt Hbf, just get there 15 minutes early and the trains will be sitting in the station and you will have a good chance of getting seats. Also, on weekends, you can travel before 9 am and still use the Brandenburg-Berlin Ticket for 29 EUR.