I go by birth dates. They are a year older when they are a year older! For the grade horses, I call them their age April 1st, assuming its a close enough bet.
Hahaha Hunters birthday is April first, but that is a guess as we are not entirely sure. I think the vet just picked that cus he is a little brat and April fools day seemed like the right choice. Lol He will be 5 wow already!