Tina's birthday is on April 30th, like mine!
She uses to celebrate it properly before the age of 14 with her friends and family, but after that, she became too busy and couldn't make time for it, she even forgot it a couple of times due to her champion duties.
After her retirement, she began to slowly but surely get back to celebrating her birthday, but it's usually with really close friends and nearby family with a simple meal and outing, nothing very fancy.