You can receive your horse as early as your first day on the farm. If you walk onto Green Ranch sometime in the Spring, Ann will give you a colt to keep. It will take a total of one season (20 days) for your colt to grow into a horse. During this time it may not be ridden and it will not wear saddle bags.
To gain it's affection brush it, talk to it, whistle for it, and ride it daily. Alternatively, you will lose affection if you hit it with a tool and you will automatically lose an affection point every night you sleep.
After growing into a horse it may participate in horse races in the Spring and Fall. These festivals will happen on the 17th of Spring and Fall from 8am to 5pm.
The day before the festival you will be asked if you want to participate, you may either accept or decline the offer. On the festival, their will be three races. The first will start at 10am, the second will start at 1pm, and the third starts at 4pm.
During this festival you may not shop.