This is 40: 40-year-old Carlos Beltran homered off 43-year-old Bartolo Colon

Bartolo Colon has had a remarkable 20-year career with a tremendous amount of highlights to his name. However, starting pitchers don't last two full decades in the Majors without giving up their fair share of homers. Colon ranks 16th all-time in home runs allowed, and nine of the pitchers who have allowed more are in the Hall of Fame.
It's not every day that the 43-year-old surrenders a homer to someone close to his age, though. On Tuesday night, the Braves faced the Astros in Houston. With the 40-year-old Carlos Beltrán in the starting lineup, it led to a rare showdown of quadragenarians.
It didn't take long for a winner to emerge, as Beltran took Colon deep in the first inning, immediately after a three-run homer by Carlos Correa.

In fact, like a radio station, Colon gave up homers to players from the '70s (Beltran), '80s (Josh Reddick) and the '90s (Correa). That's impressive -- in a way. 
The Astros went on to win the game, 8-3. Afterwards, Beltran jokingly called the matchup an "old battle," noting Colon's extensive experience. "I have to give him a lot of credit. He's been in the league for a long time, and he has been able to reinvent himself," said Beltran to MLB.com's Brian McTaggart. "I've faced him a lot. ... I got a sinker on the inside part of the plate, and I was able to stay inside and got a good result."
After all, Beltran has had plenty of time to work on his approach against Colon. In their very first matchup, all the way back in 1998, Colon struck Beltran out: 

Another testament to Colon's longevity is the fact that this wasn't even the first time a 40-year-old had taken him deep since his own 40th birthday. Beltran's roundtripper was the first "40-on-40" homer since Raul Ibanez went yard off Colon on April 13, 2014. 

Coincidentally, the Ibanez blast was also part of a string of homers against Colon. The Angels did the Astros one better on that night -- Mike Trout, Albert Pujols, and Ibanez went back-to-back-to-back. 
Colon has truly seen it all.