There’s a post-Blip poster near the film’s start.
When Shang-Chi heads to Katy’s house for breakfast, focus on the left side of the screen. Right before he opens the door, there’s a wall full of posters.
Among them is a sign offering help to those struggling to adjust with life post-Blip. The poster reminds people that they’re not alone and mentions a hotline.
The moment occurs soon after Shang-Chi and Katy catch up with their friends.
The math adds up, for the most part, if we make an assumption that Shang-Chi was born around 1998.
Xu Wenwu (Tony Leung) meets his future wife, Li (Fala Chen), in 1996 near the film’s start.
We later learn that Shang-Chi left home around 14/15 and has been on his own for 10 years, the amount of time Katy (Akwafina) says she’s known him.
Later, Wenwu says he gave Shang-Chi a decade to live his own life before he sought him out. According to that math, Shang-Chi should be about 25.
“Avengers Endgame” takes place in 2023. If we assume Shang-Chi wasn’t born in 1996, but two or so years later, that would bring “Shang-Chi and the Legend of the Ten Rings” to 2023 as well.