It hit #1 on the chart date of August 7, 1976. I was born on August 6, 1976. Therefore, the Manhattans were still #1 until the day after I was born.
Now, if you want to get technical, the sales and radio airplay data used to compile the chart was actually collected at least a couple weeks prior to that, so the "real" #1 of my birthdate would be reflected in the chart a couple weeks later, but that's a little too pedantic even for me.
This is an interesting argument as to when the songs become #1. Are they #1 after it is announced, or were they #1 during the previous week when they were tallying up the numbers leading up to the day it was announced? I am inclined to go with the former, but Billboard seems to disagree. I mean, the Phillies are the 2008 World Champions of Major League Baseball, but they weren't until they won the World Series. It's retroactive to the season in which they ended up winning, right? In any event, I was born on August 30, 1982. On August 28, "Eye of the Tiger" by Survivor was #1. "Abracadabra" by Steve Miller Band took over at #1 on September 4. I'd prefer Survivor of those two (Rocky III theme song, of course). "Abracadabra" has that awful rhyme in the chorus ("I wanna reach out and grab ya!"), and it was not nearly as good as the mid-'70s stuff. In the UK, "Come on Eileen" by Dexys Midnight Runners was #1. That's a lot better, although I like some other Dexys songs better than that one ("Geno," "Dance Stance"), but it's a much better single than the American hits.
Who wants to try a bottle of merc's "Extroversion Olive Oil?"