[tz] Irish Standard Time vs Irish Summer Time

Philip Paeps philip at trouble.is
Fri Jan 19 05:44:15 UTC 2018

On 2018-01-18 19:39:50 (-0500), Tom Lane wrote:
>Zefram <zefram at fysh.org> writes:
>>There was indeed a significant chance of the negative SAVE value 
>>breaking alternate zic implementations, and now that that's turned out 
>>to be the case that's good cause to postpone this correction, or at 
>>least the expressing of it in this natural manner.  The tzdb does have 
>>unusually high stability requirements.  But that's not a reason to 
>>keep the database forever inaccurate.
>I'm not sure that it's "inaccurate".  The question is more about what 
>is the meaning of tm_isdst = 1.  It's clear from this discussion that 
>an awful lot of code believes it means "local time is advanced now 
>compared to what it is when tm_isdst = 0".  Arguing that it should 
>reflect a legalistic definition of DST, rather than an operational 
>definition, is just an argument; it's not conclusive.
>FWIW, I share the opinion that this change was misguided.

I'd go with "premature" rather than "misguided".

Given the number of things this break, I would suggest backing the 
change out for now but pointing out in NEWS that it will come back say 
one year from now.

Replace the actual change by a comment that the current data is 
inaccurate pending software being fixed.


Philip Paeps
Senior Reality Engineer
Ministry of Information

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