Science
This Is The Right Way to Calculate Dog Years – Lifehacker Australia
The underlying assumption is that each calendar year a dog lives though is equivalent to seven human years at any stage of a dog’s life.

Your pup may be older than you think.
If your dog has been alive and kicking its paws about for a decade, the widely held belief is that it has aged as much as a human would have done by the grand old age of 70. This conversion factor each year of a dogs life accounting for seven human years comes from dividing human life expectancy of around 77 by the canine life expectancy of around 11.
The underlying assumption is that each calendar year a dog lives though is equivalent to seven human years…
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