I think Ilya had a lot of forgotten/low key birthdays.
I think he was so frequently at summer training camps after his mother died that it went unacknowledged. Maybe a cupcake if someone made note of it.
Even when he's an NHL superstar he gets bland texts from teammates, classic PR public birthday wishes, and gets drunk in Russia, usually with Svetlana. She gets him a card and several years in a row she takes him to a friend of a friend who breeds working farm dogs and lets Ilya dissociate with a bunch of puppies.
Then, after the Olympics, Shane actually texts him "happy birthday". With a little balloon emoji.
It makes Ilya's month. Even if he doesn't show it when he sees Shane a couple weeks later in Vegas.
Then, in 2015, Shane texts Ilya "happy birthday" at midnight in Boston, so perfectly timed that he's sure Shane set an alarm for it because he's in Halifax with the Metros and the Cup doing a cross-Canada victory tour. And that makes him so warm and fuzzy.
In 2016 Shane texts him "happy birthday" at midnight, and this time there's a picture. A screenshot of a donation made by Shane to a Russian community centre in Montreal. Ilya looks up the centre and they're the one place that gets a pass on cheering for Boston in the whole city, because so many of the young Russian kids look up to Ilya. In the spot to list a reason for the donation Shane's written "for Lily".
In 2017 Shane texts him a plain happy birthday. But then he has a proper cake (though small) ordered from a small bakery near the cottage. It's set for delivery a couple days after Ilya arrives (the day after they come out to Shane's parents) because it gave him enough time to cancel if it went horribly.
So Ilya wakes up to find Shane not in bed, talking politely to someone at the door, and when he goes to see what it is he finds Shane standing with a plain white box that he gingerly sets on the table and opens to reveal a beautifully decorated cake. It's a soft blue frosting with chocolate ganache covering the top and dripping down the sides, there are chocolate covered strawberries perfectly spaced on the top.
"I wasn't sure what flavour you'd like so the top layer's funfetti, the middle's chocolate, and the bottom is strawberry. And there's cookie dough-flavoured icing in the middle."
It's enough cake that between the two of them and Shane's parents it takes them a week to get through.
It becomes a thing. Shane finds new cake flavours for Ilya's (belated if the awards are after his birthday) birthday cake every year.
When they finish their first season together on the Cens Shane has spent months working with Harris in secret. And Ilya's birthday is turned into a Centaur's community fair. They fill the parking lot with rides and free carnival food and games. There's a massive adult-sized bouncy castle.
And there are twenty different flavours of sheet cake, each one with a different letter/number/! spelling out "Happy 31 Birthday Ilya!"