We have all heard it before: every dog year counts for seven human years. The myth has been around for a long time without any evidence to back it up.

Now, researchers at the University of California San Diego School of Medicine have created a new formula that more accurately calculates your dog's real age. The formula relies on the changing patterns of methyl groups in dog and human genomes.

It takes into account the rate and location of these chemical tags as they age and throws the old 1:7 rule of thumb out the window. The scientists say it does more than dispel a long-held myth, it may actually provide a useful tool for veterinarians, and for assessing anti-aging intervention options.