The further advance notice you can give, the better.
I like to give – and receive! – advance notice because it helps to make sure people can shuffle their busy schedules and participate to the best of their ability.
I also like to give advance notice because, when someone comes last-minute and says they can’t attend, I can remind them of exactly when they received their calendar. It’s small comfort, but it’s a comfort.
Conversely, I find it incredibly frustrating when I get notice of calendar dates at the last minute, and can only imagine that my students and colleagues feel the same.