I am not in favour of alphabetic abbreviations as designators of time zones. First, their role is not well defined. Do they apply to A: a geographic region and its entire time-offset history and future, B: a particular single offset from UTC/GMT, or C: a particular set of two or more offsets from UTC/GMT and "rules" describing when changes from one of these offsets to another occur? Second, there seems to be no requirement for them to be globally or historically unique. I would support two types of time-offset designation: 1: a numeric specification of a single offset from UTC/GMT (e.g. -04:00) 2: a specification applying to a point on the earth's surface and indicating the entire history (and expected future history) of the time kept at that point by nearby human beings, as in the tz database (as I understand it) Actually, I might also consent to: 1A: a numeric specification of two (or more) offsets from UTC/GMT that apply periodically (e.g. +10:00/11:00), though only if such a specifier is unique in the context it is used in (+10:00/+11:00 applies both to Tasmania and mainland southeast Australia, but the two regions change from +10:00 to +11:00 at different times at present, so using that label for a zone as things currently stand would not be on) 2A: a specification applying to a well-defined, invariant region of the earth's surface and indicating the entire history (and expected future history) of the time kept by human beings occupying that region Type 1 is by far the easiest to work with, and perfectly adequate for single-instant specifications. Only if, for a particular geographic location, a period of time (including possibly a single date) or a repeating scheduled event is to be specified might a single offset not be up to the task. If some apparent standard abbreviated designator is not clear, a lot of effort seems to be put into crafting a "suitable" one for the field labelled (for reasons that aren't all that clear to me) "FORMAT" in the tzdata files. I get the impression that people derive a sense of security from the authority and credibility supposedly lent to time specifications by such labels. Only it is a false sense of security, I would contend. These abbreviations seem to be seized upon by implementors of time-management software as though "official" and indispensable and to be appended enthusiastically to time specifications. I would like to see such enthusiasm diverted to the use, instead, of far less ambiguous and far more informative and helpful designators (like type 1 especially). (I realise now that I have somewhat conflated time zones with time specifications. I don't think my comments are affected that much by this.) I hope I haven't strayed into territory outside the purview of this list.