Comment by AgentME

ChatGPT will reveal the correct current date if you don't ask for it directly but ask for an answer that involves the current date. (https://twitter.com/goodside/status/1598890043975774208)

I think what's happening is that part of its prompt tells it that if it's asked for any contemporary information, then it should explain to the user it doesn't know that because its knowledge of the world is based on when it was trained in 2021, and asking for the date triggers this, regardless of the fact that it does actually know that answer.