Dog years refer to a popular myth that household pets—specifically dogs and cats—age seven years for each human year. For example, a dog of age 9 would be said to be "63 in dog years".

In technical terms, this is not correct: Most household pets do not age in any linear correspondence with human aging. Dogs and cats age much more quickly in their early life than in their later life relative to humans. For example, the human equivalent of a 1-year-old cat or dog is actually about 14 to 15 years, and the second year is equivalent to about another 7 or 8 years, and each year thereafter is equivalent to only about four human years.

In the comedy Red Dwarf Holly tells Lister that he could serve a two year prison sentence in just fourteen weeks by becoming a dog. Lister wasn't impressed.

- From Wikipedia, the free encyclopedia