[tz] Inappropriate project direction

Robert Elz kre at munnari.OZ.AU
Sun Feb 11 10:20:21 UTC 2018

    Date:        Sun, 11 Feb 2018 10:36:57 +0100
    From:        =?UTF-8?B?TWFyayBEYXZpcyDimJXvuI8=?= <mark at macchiato.com>
    Message-ID:  <CAJ2xs_Gjg4ioTx=DG-4xYBfrTnNhUiNLkb2CR=8ATbPT88z2FA at mail.gmail.com>

  | Why does that make any difference to a user?

Depends upon the user, and what they are doing.

Consider a user with an app in which the user can enter a date & time
for some purpose (calendaring, or whatever).  Suppose the user happens
to enter the time during the period when the clocks have just switched
backwards (the period of ambiguity) so the app, being a well written
(and posixified) app, asks the user whether "standard time" or "alternate time"
was intended.   The user, in Eire, wants "Irish Standard Time" so they
reply "standard" (as would anyone sane).  The app then sets tm_isdst to 0
and re-does the mktime() which (as things are now) will generate the "GMT"
UTC equivalent time, instead of the "IST" version, exactly the opposite of
what the user intended.    It does matter.

  | Why do people think that the name  has to be aligned with that flag,

The name obviously doesn't (in Eire, it could be in Gaellic) - but the concepts
need to be applied correctly.

The value of tm_isdst from localtime()  should be simply regarded as
noise, it is of no value whatever.  But the uses of tm_isdst (badly named as
the field is for the purpose) in mktime() are both valid, and useful, and for
that it needs to work correctly.


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