While equines from the north enjoy their special day on January 1, both standardised dates are based on the breeding season in order to keep the racing industry fair.

The day will be extra special for 1992 Melbourne-cup winning racehorse Subzero, who will be marking his 30th birthday milestone.

The stalwart grey has spent his retirement visiting more than 100 schools, 35 retirement villages and 30 unique charities every year.

Champion mare Winx will celebrate her seventh birthday this year, after ranking top of the world following her 25th-straight Queen Elizabeth win, and 18th at Group One level.

Other Melbourne Cup winners including Might and Power and Prince of Penzance will indulge in special treats at an event in Greenvale, where the Melbourne Cup's 18 carat-gold trophy worth $200,000 will also make an appearance.

"A lot of people don't keep records on horses exact birthdays, so within the horse racing industry it helps to have the same birthday every year," a Glenworth Valley spokeswoman told AAP.

Every year Glenworth Valley horses are given an unbridled birthday gallop in a freshly seeded paddock.

NSW Minister for Racing Paul Toole wished NSW horses a happy birthday ahead of the spring racing carnival.

"I'm particularly looking forward to the first running of The Kosciusko, the richest country race in the world, which will be run at Royal Randwick on Everest Day," Minister Toole said in a statement.

Australian Associated Press