Ever wonder how old your favorite rock star is? Or, more specifically, how old a computer thinks they look?

One of the coolest new on-line distractions has a lot of folks uploading photos to how-old.net, which hopes to guess your gender and age using face-recognition software. This is still developing technology, and the programmers have already admitted that, so far, "it isn’t particularly accurate with age." They're quick to add, however, that "it’s often good for a laugh and users have fun with it."

Certainly, that's true in the photo gallery we've compiled above. The so-called How Old Robot was remarkably accurate with stars like Sammy Hagar, Vince Neil, Tom Petty and Neil Young, but struggled with others. It had Joan Jett, Ringo Starr and bandmates Joe Perry and Steven Tyler much younger than they actually are.

Others, the program guessed to be much older than in real life – including Joe Elliott and (in the most shocking discrepancy in our trial) poor Robert Plant. You won't believe how old the software thought he was. Click through the gallery above to find out how old this program thinks your favorite rock stars look.

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