Dog years and cat years. This is a concept created for the truly stupid.
The year itself doesn't change just because it's from the prospect of a different animal. Time is a constant. Different organisms have written in thier DNA a great many things. How they grow, thier instincts, thier appearance, everything including thier lifespan. These genetic codes vary, so the lifespan varies as well. No two people are actually generically coded to live for the same amount of time, never two species. These dog and cat years are for people who understand the basics of life. Dogs and cat's don't live as long as people, it's that simple. Seriously, how stupid do have to be not get that 13 year old dog is quite old just a because a 13 year old human isn't considered old?
Still, if people insist they this metaphor to understand this incredibly simple premise, then I say why stop with just Dogs and Cats? How about Redwood year or Giant Tortoise year. Or on the other end of the scale, how an Apply year or a house fly year? Or maybe it would actually be easer to just understand that the human lifespan is a not fucking calendrer.