Originally Posted by Pedigree Ann

Correction - Horses in former British possessions in the Southern Hemisphere (Australia, New Zealand, South Africa) turn a year older on 1 August each year. In South American countries, like Argentina, Brasil, Chile, etc., they turn a year older on the more logical 1 July.

The big thing about second-half 3yos from the SH who race in NA as 4yos (Jan to June) is that they don't get any weight concession for their lack of maturity. While winning the Pimlico Special, Invasor was actually a 3yo but was carrying weight appropriate for a 4yo. By the time of the Suburban in July, he was officially 4 in both SA and US, although not actually 4. So now his official age in both hemispheres and his actual age all correspond. How Lovely.