[tz] User time zones

Guy Harris guy at alum.mit.edu
Thu Dec 8 18:38:47 UTC 2011

On Dec 8, 2011, at 10:12 AM, Eric Muller wrote:

> I don't quite see any other solution than storing a time together with the timezone in which it is expressed.

Where by "timezone" you presumably mean "reference to an Olson database entry" or, as you use later, "tz timezone".  "June 17, 2012, 11:00 in the Mountain time zone" is insufficient information to generate a UTC date - you don't know whether it's in Arizona or not.

> There is the subsidiary issue that what people really need is "the timezone of this location", rather than "this tz timezone". The difference shows up in the tz database whenever a new tz timezone is introduced. Fortunately, such changes are much less frequent.

...and solving that problem involves perfectly predicting the future, i.e. it's impossible.

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