The very first slide of your presentation is what is called the welcome slide; the one with the topic of your talk and your name on it. I've written a bit about it in Presenting for Geeks, but presenters are doing it right most of the time automatically. Except, maybe, for one little detail ...
The welcome slide usually includes the name and date of the event for which the presentation was created. And presentations are sometimes reused. There's nothing wrong with this. Except when you forget to update the welcome slide and it still refers to a past event.
I'd bet that anyone attending conferences has come across a presentation like that. You now know that you get to see something that wasn't made for you or for the specific audience in the room. It immediately makes you feel less appreciated. And it would be so easy to fix!
I encountered a variation of this issue at an event recently, when the speaker apologised that the welcome slide featured a date just a few days ago. She went on to explain that she had originally been scheduled to give this talk at a similar event but that didn't work out for one reason or another, so she was giving the talk to this audience for the first time.
None of this was relevant to this audience at this event, though. If she had just updated the date on this one(!) slide and never even mentioned the other event, we would all have been perfectly happy with the talk. Not to mention that she could have used the time she spent on this introduction on something relevant to the topic of the talk.
It's only a little thing, so it tends to get overlooked. But please do make sure your welcome slide reflects the current date and event. Then you don't even have to mention it at all in your talk.
Please email me for details.