I’m curious as to why the Left used that date. One thought is that they figured out that the computers wouldn’t flag it as double-voting, since there are no real voters that old (other than 1 or 2, maybe).
Having worked in computer systems, there are instances when the DOB isn’t known and not entered, and it defaulted in 1/1/1901.
When I see that, I see a workflow issue. That is, the DOB is a required field, something has to go in there, and someone wrote the software to default in 1/1/1901, and you could just skip over it when entering the demographic data.