For cats, I understand that this is a far more accurate estimation than the tradition 1 year = 7 concept, which would have made Cutie more than two hundred years old at her death, which seems unreasonable.
I have never seen an accurate charting of age-human for dogs either. I've seen some dogs who were frisky as all get out at 13 and I look at my Marley who at age 8 was already like, "what, you expect me to move?"
I was told by a Veterinarian that there is no correlation between the age of an animal and that of a human. When we had to have our beloved Yellow Lab Daisy put down at age 14-1/2, people asked..."How old is that in human years?" I calmly replied "Fourteen and a half years." A year is the same for all Humans and Animals: 365-1/4 Days. (Those 1/4 Days cause a Leap Year every 4 years, don't ya know.) Howl