That kind of phrasing is boilerplate for indictments. It's used even in the most nailed-down circumstances. Here's a bit from Zacarias Moussaoui's indictment for 9/11 [0]:
> On or about September 11, 2001, Saeed al-Ghamdi, Ahmed al-Nami, Ahmed al-Haznawi, and Ziad Jarrah hijacked United Airlines Flight 93, a Boeing 757, which had departed from Newark, New Jersey bound for San Francisco at approximately 8:00 a.m. After resistance by the passengers, Flight 93 crashed in Somerset County, Pennsylvania at approximately 10:10 a.m., killing all on board.
I mean, if they're being careful about the date of that, they'll do it for all dates. (Curiously, though, the very next paragraph in that indictment doesn't use the "on or about" qualifier.)
I think it means "we have evidences about his crimes in 2019, but we suspect he also commited some crimes earlier, and if we'd find additional information in due course, we reserve the right to add it to the charges" in legalspeak.
It prevents the defense from using the precise language as a technicality.
“You honor, my client is accused of crimes starting in 2019, but we intend to show that the fraud started in 2013. That is completely different crime which this case does not address. Motion to dismiss”
That probably wouldn’t work, but why take the risk?
IANAL, but I did serve on a criminal jury once. Not that it means much. When we got instructions for how to render a verdict, every charge was explained in plain English, maybe one or two sentences, and definitely included the date. It seems to be a technicality that matters, and someone could walk if the date is wrong.
The “in or about” is separate, and means they found things that may have been in 2019 but are not foreclosing that those particular things may have occurred at a different time
