In the Northern Hemisphere, all Thoroughbred horses have the same official birthday on January 1, regardless of their actual date of birth. In the southern hemisphere, all thoroughbred horses share a birthday on August 1. The goal of giving all Thoroughbred horses the same official birthday is to more accurately categorize them by age for racing. This birthday rule means that a horse born in mid-December would officially be 1 year old less than a month later, on January 1st. Breeders normally try to have their horses born as soon as possible after the official date to give them as much time as possible to train them for the race. Once a Thoroughbred horse reaches its second birthday, it is usually eligible for racing.
More about horses:
Horses cannot breathe through their mouths, only through their noses.
A horse expends more energy when lying on the ground than when standing.
Thoroughbred horses can run at top speeds of more than 40 miles per hour (65 km/h).