Clearly in most cases time should be store in UTC. And in all cases a datetime that records a past event should be stored in UTC. We do this because civil time keeps changing and an event happened at a moment that's detached from whatever the local government thinks the time is.
But when times are detached from dates, when they refer to wall-clock times, I contend that they should be stored in wall-clock time.
Let's say I have a system that has to perform an event at 3pm in a particular time zone, I contend that I'm best to store the time as 3pm. This is even more true when the event is recurring and should always occur at 3pm -- whether daylight savings is in effect or not. And if it should occur for multiple users in various time zones at 3pm-local, storing anything in UTC just seems silly.
To me, this feels obvious. But I'm looking for a standard, a specification, or at least a blog post from a trusted source that can back me up.