Number of people that were alive during the last two comings of Halley's comet: millions

Number of people who were alive the last time this happened: at least 76. Including this woman. It's probably safe to say that none of them remember.

Edit: As soon as I published this post, I noticed a freaky coincidence: 76 is the length in years of Halley's comet! Okay, it's only a coincidence because I chose that as the comparison, but nevertheless, it freaked my mind (it doesn't help that Criss Angel is my office-mate).