HGG Community Forums

The last midnight of the month the game closes down for an hour or so and all horses age up by one year.

I know it can be overwhelming because there’s so much information but the FAQ link in your side menu is a really good place to start looking for information. The following is copied straight from it:

When will my horses age up?

One real life month equals one year on Hunt & Jump. Horses age up at the start of each new "year", so, at the beginning of the next month your horse will age one year.

Newborn horses are listed as foals but will age up to yearlings in a few days. Most of their first real life month will be spent as a yearling. They will turn 2 when the beginning of the next real life month rolls around.