In Australia, all thoroughbred horses have their birthdays on the first day of August.

The local equine community won't rein in the celebrations tomorrow.

The Southern Highlands Vaulting Team (SHVT) has planned a birthday party for its three horses at the team's base in Alpine.

Tigger will turn 18 years old and Morgan (17) and Cognac (16) will also be recognised.

SHVT volunteer Amanda Lee said International Horse Day was important on the equine calendar.

"It's a mandatory birthday for horses in the thoroughbred industry," she said. "It's a day that everyone takes on board and celebrates.

"September 1 is the milestone day for trotting horses."

The SHVT is open for children and has around 20 members.

Ms Lee said the SHVT members looked forward to the occasion.

"We will have a little birthday party, bake cakes and get a little present for our horses," she said. "It's like a children's party but aimed at horses."

Bowral Dressage Club events secretary Leah Brown said the club didn't have a celebration planned tomorrow.

However, Ms Brown said International Horse Birthday was important on the horse events calendar.

"Dressage is an Olympic discipline so we have a focus on the age and breeding of our horses - we know their specific birthdays," she said. "We generally don't do anything to celebrate, it's more of a thing for juniors."