Babies at the Movies

My wife and I went to the movies last night, and, as we were getting ready to enjoy the flick, in strolls a family with a baby whose age could only be measured in months. The surprising thing is that the baby was incredibly well behaved and didn’t make a peep throughout the entire film. My question is: how young is too young to take a kid to the movies? Because even though I was proven wrong this time, I would guess less than a year old is a little on young side.