Whats the story behind dog years?

We’ve grown up believing that one year of a dog’s life is equal to seven years of a human’s. While dogs do age at a more rapid rate than humans, seven isn’t the magic numbers. In most breeds, the first year of a dog’s life is equal to 15 years due to how rapidly they mature. The calculation for the rest of the dog’s life really depends on the breed, as some dogs will age much faster than others.