[icu-design] System time zone detection on unix platforms

[Pulbere, A. <Ale...@co...>]

Recently we've encountered a problem were dates are not formatted
correctly on unix platforms because the default time zone is not
determined correctly.
For example: date/time values which are in DST range for Estern Time,
when formatted FULL type always have "EST" as timezone.
On unix platforms the timezone ID is obtained from tzname[0] array,
which always returns the "standard" abbreviation of a timezone: EST,
CST, PST, etc.
A solution to this problem would be to implement a map similar to the
one implemented for Windows platform.
The difficulty is that, on unix, timezones that have different DST rules
but use the same offset might be represented by the same "standard"
abbreviation.
For example: America/Regina and America/Chicago, both use CST for
standard time. In this case the DST abbreviation might provide a key to
differentiate them.
Because of that, both standard and DST abbreviations should be used to
try and determine the ICU timezone.

I'd like to ask if ICU dev. team has anything in mind on how to address
this problem and what do you think about the approach described above.


Alex Pulbere
Software Engineer
Cognos Inc.=20
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