Do All Horses Have the Same Birthday?

The official birthday of thoroughbred horses is January 1, regardless of
the actual day they are born.

In the Northern Hemisphere, all thoroughbred horses have the same official
birthday of January 1, regardless of their actual date of birth. In the
Southern Hemisphere, all thoroughbred horses share the birthday of August
1. The purpose of giving all thoroughbreds the same official birthday is to
more accurately categorize them by age for racing purposes. This birthday
rule means that a horse born in mid-December would officially turn 1 year
old less than a month later, on January 1. Breeders typically try to have
their horses born as soon as possible after the official date, in order to
have as much time as possible to train them for racing. After a
thoroughbred horse reaches its second birthday, it generally is eligible
for racing.
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