If you're going to make a mistake, don't make it on slide one.
A lot of times when we build slides, we're working off an old template and updating it for the current situation. It's easy to forget small details on the first slide, like updating the old date.
It seems minor, but it takes away from the credibility of everything that follows. It makes the reader question how much care went into the rest of the deck.
I've made this mistake myself. Back in my investment banking days, I learned fast never to let it happen again. Maybe that's why I still have a visceral reaction when I see an obvious typo on slide one.
Mistakes and typos happen. But if they must happen, don't let them happen in the first thing your audience sees. First impressions matter even in PowerPoint, Google Slides, or whatever you use for your decks.