How old is that in dog years?

This puppy was photographed in 1845, which would make it 164 years old.

The photo, "Harriet Farnie and Miss Farnie with a Sleeping Puppy, Brownie" is from the National Galleries of Scotland's photostream, now available on Flickr.

Robert Adamson, David Octavius Hill

1920 (original negative around 1845)

Accession no. PGP HA 390
Medium Carbon print
Size 15.40 x 20.20 cm
Credit Elliot Collection, bequeathed 1950