ECMA-402 now supports short-offset, long-offset, short-generic, and
long-generic time zone name formatting. For example, in the en-US locale
the America/Eastern time zone would be formatted as:
short-offset: GMT-5
long-offset: GMT-05:00
short-generic: ET
long-generic: Eastern Time
We currently only support the UTC time zone, however. Therefore, this
very minimal implementation does not consider GMT offset or generic
display names. Instead, the CLDR defines specific strings for UTC.
The parsing in parse_calendar_symbols() might be a bit more verbose than
it really needs to be, but it is to ensure the symbols are generated in
a known order that we can control with enumerations.
Unlike most data in the CLDR, hour cycles are not stored on a per-locale
basis. Instead, they are keyed by a string that is usually a region, but
sometimes is a locale. Therefore, given a locale, to determine the hour
cycles for that locale, we:
1. Check if the locale itself is assigned hour cycles.
2. If the locale has a region, check if that region is assigned hour
cycles.
3. Otherwise, maximize that locale, and if the maximized locale has
a region, check if that region is assigned hour cycles.
4. If the above all fail, fallback to the "001" region.
Further, each locale's default hour cycle is the first assigned hour
cycle.
