Well, usually what you want is actully the UTC offset, not the timezone, because that's what you need to get the actual-wall-clock timestamp of the event. If you all you have is a timzeone, then you need an accurate historical tzdata and also you need to be sure that the system had accurate tzdata itself when it produced the timestamp.

Of course, if you're storing the timestamp of a future, planned event, then yes, you need a timezone. But for historical records, store the UTC offset that was in effect when the event happened.