Why your dog isn't the age you think

First of all: Props for fact checking such a myth. It's far easier to accept such a piece of information as given. I would like to see this kind of thinking far more often! Unfortunately, without sharing the source this piece of information is as credible as the one before. (source: someone once told they read it somewhere).

The question "How do they quantify aging?" is a topic they most likely covered in the paper the results are from. An additional short summary of the methodology would even give people that don't check the source a feeling about the crediblity. The fact that you ask that question is kind of a red flag in science communication, because it seems to me that you cite a research result without a basic understanding how it was measured.