The English language contains a great number of colloquialisms and idioms that don’t necessarily make much logical sense. It can’t literally be raining cats and dogs, but you could care less. Some of these bother me more than others. One concept that has always rubbed me the wrong way is the idea of “dog years” and how they differ from, you know, regular years.
As a general rule of thumb, people have come to equate a single dog year with seven human years. There are some more complex formulas out there that so-called “experts” may prefer, but we’ll stick with the 7:1 ratio for the purposes of this post. The idea is that the average life expectancy of a person is roughly seven times that of his or her canine companion.
This is hardly an exact science and there is going to be a great deal of variation. Taken as a whole, a domesticated dog can expect to live about 13 years. Some breeds can expect to live longer and some breeds can expect to lead shorter lives. If we extend the 7:1 ratio here, then we can say that the average human being can expect to live 91 years. That’s probably a little on the high end — the highest life expectancy would be that of a woman in Japan (87) — but we’ll just accept that at face value.
Given this, if you were to encounter a golden retriever who was five years ago and you were asked what that would be in dog years, simple math would reveal that Fido’s “age” is actually 35.
The problem that I have with people talking about “dog years” is that “dog years” don’t exist. The concept or length of a year is not based on how long a person (or animal) can expect to live. The length of a year is based on how long it takes a planet (in our case, the Earth) to complete its orbit around a star (our Sun). That is the very definition of a year; a year on Earth is currently about 365.24 days, bearing in mind that the notion of “days” is also relative. An Earth day is not equivalent to a Martian day, for example.
If we were to base a “year” relative to human life expectancy, then a year for someone living in Sierra Leone (where life expectancy is about 46 years) would be different from a year for someone living in Canada (where life expectancy is about 82). Talking about “dog years” is almost as offensive as talking about Norwegian years, Turkish years or Somalian years.
Some of you may say that I’m nit-picking and the English language is something that continues to evolve over time. That may be true. Even so, I still maintain every right to wince when I hear someone talking about “my Friday” or “dog years.” It’s just not right. Don’t do it.