Third point is worded really unclearly. GMT still = UTC (modulo seconds point that has been made elsewhere). BST = GMT + 1; British time is either GMT or BST depending on the time of year.
Advice to display an offset when displaying a time is wrong or at least incomplete; you should display a symbolic timezone (i.e. "London" or "Eastern US" etc.) as that's what's going to be meaningful to someone reading it.
Advice to display an offset when displaying a time is wrong or at least incomplete; you should display a symbolic timezone (i.e. "London" or "Eastern US" etc.) as that's what's going to be meaningful to someone reading it.