Select the QQ friend you want to view in the friend list, and put the mouse on that person's signature for about one second, and a box will appear with the signature inside and the word "more" at the bottom of the box. Click these two words, the scroll will be opened, and the update time of friends' signatures can be seen in the list.

If QQ is a relatively new version, and I suspect that LZ is making me passively publicize, I can't keep my privacy.