Does any one remember the logic behind sp->goback and sp->goahead in localtime.c?

Kevin Kenny kkenny2 at
Sun Jan 13 02:52:39 UTC 2008

Jonathan Leffler wrote:
> AFAICT, the logic associated with sp->goback and sp->goahead in tzload() 
> and in localsub() in localtime.c could only ever be used if there were 
> at least 800 time change entries, enough for two per year for a 400 year 
> cycle.  And, empirically, there are no time zone definitions in the 
> current (2007k) data set that get anywhere close to this.
> However, this code can't have been put in there for no reason 
> whatsoever, so I'd like to understand what was the intention - if 
> anybody can remember.

I'm not positive, but I *think* that it was an effort to support solar
time in the Arab countries; solar time was approximated by making
several hundred time zone changes *per year*.  The legacy 'solar87,'
'solar88' and 'solar89' files in tzdata show what was being tried.

7e de ke9tv/2, Kevin

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