When I was Scoutmaster, I had one boy show up at 9:00 on the night before he turned 18 to finish up his Scoutmaster's conference and get his paperwork all in order (you have 3 months after your birthday to have your board, and can get an additional 3 months with special approval (stuff happens sometimes)).
Everything was finished and ready to go for his board of review at 11:30 p.m.
That's the closest call, but there were several others within the last week of their 18th birthday.
