What is the correct nomenclature for timezones?

Question

There are different ways of identifying the same timezone, which can each be used by different programs in different ways. I live in Wisconsin, so we generally refer to the timezone here as "Central Time." But I know that Windows has a registry entry for Central Standard Time, which in fact is actually comprised of both Central Standard Time (CST) and Central Daylight Time (CDT). But more recently I've seen this timezone displayed as America/Chicago.

What are the right terms to refer to these two different standards? So for instance, what do you call the America/Chicago way of identifying the timezone? Is that something like the "Standard TZ Info name" or the "ISO-1234567 timezone name" or the "Eggert TZ name"?

And what about the slightly more familiar Central Standard Time? Do you refer to that syntax as the "Friendly timezone name", or the "ISO-987654321 timezone name", or something like that? Thanks!

Answer 1

There are no exact standards for the nomenclature, but here are some guidelines:

• Time zones like America/Chicago are commonly referred to as "Olson Time Zones", "IANA Time Zones", or "TZ Database Time Zones". There is some background on Wikipedia with the history of the database that explains some of this.

  • "IANA Time Zones" is probably the most correct form these days, as the project now resides under the stewardship of IANA.

  • Occasionally, you'll hear them referred to by the language that uses them, as in "PHP Time Zones" or "Java Time Zones". This usually comes from a lack of understanding about the implementation, and I would discourage using these names.

• The time zones in the Windows registry are commonly known as "Microsoft Time Zones" or "Windows Time Zones".

  • I'd actually encourage calling them "Legacy Windows Time Zones", as IANA time zones are slowly making their way into Windows, such as with the WinRT classes: Windows.Globalization.Calendar and Windows.Globalization.DateTimeFormatting.DateTimeFormatter.

  • I sometimes hear them called ".NET Time Zones", or "TimeZoneInfo Time Zones", based on their usage within the .NET Framework, but I would discourage this sort of naming.

  • Pay no attention to the naming conventions of the Windows time zone identifiers. They are all over the place.

Some of this is also covered in the 'timezone' tag wiki.

Oh, and since we're talking about naming, it's "time zone" (two words), not "timezone". :)