Time Zones

Reflections on low-level ontology primitives.

We had a workshop last week on gist (our minimalist upper ontology). As part of the aftermath, I decided to get a bit more rigorous about some of the lowest level primitives. One of the basic ideas about gist is that you may not be able to express every distinction you might want to make, but at least what you do exchange through gist will be understood and unambiguous. In the previous version of gist I had some low level concepts, like distance, which was a subtype of magnitude. And there was a class distanceUnit which was a subclass of unitOfMeasure. And unit of measure has a property that points to conversion factor (i.e., how to convert from one unit of measure to the base unit of that “dimension”). But what occurred to me just after the workshop is that two applications or two organizations communicating through gist could still create problems by just picking a different base (i.e., if one said their base for distance was a meter and another a foot, they have a problem).

This was pretty easily solved by going to NIST, and getting the best thinking on what these dimensions should be and what the base unit of each dimension should be. Looking at it, I don’t think there ought to be much problem with people adopting these. Emboldened, I thought I would do the same for time.

For starters, universal time seems to the way to go. However, many applications record time in local time so we need some facility to recognize that and provide an offset. Here’s where the problem came in and maybe you dear readers can help. After about an hour of searching the web the best I could find for a standard in this area is something called the tz database. While you can look up various cities, I didn’t see anything definitive on what the geographical regions are that make up each of the time zones. To make things worse, the abbreviations for time zones are not unique, for instance, there is an EST in North America and one in Australia. If anyone has a thought in this area, I’m all ears.

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