On Sep 1, 2013, at 11:56 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:
Guy Harris wrote:
If it's an entry for Paris, rather than for the French time zone, why don't we have entries for Lyon and Lille and ...
It's because of the 1970 cutoff. We would have entries such as you describe, if we changed the cutoff to (say) 1940 rather than 1970. Europe/Paris would split into 28 zones (if we accept the Shanks data), each with its own timestamp history.
But you're probably *still* going to get multiple cities within the same zone even if you change the cutoff to 1911 or even 1891: http://vanessafrance.wordpress.com/2012/03/25/a-brief-history-of-french-time... so the question I'd ask is "why should certain cities be blessed by the tzdb by virtue of having their particular local solar mean time in the database"?
I agree that the LMT offsets are notional, but even so, requiring them to be multiples of an hour feels ahistorical. Before standard time was observed people simply didn't set their clocks to hour-multiples offsets, and it would be odd to pretend that they did.
Then maybe we should just have localtime() return NULL for times prior to the adoption of standard time (as it doesn't take a longitude argument, we can't figure out local time - and even if it *did*, as Steve Allen noted, there might be more than one local time value for a given longitude, unless the longitude indicates which of the two Kansas City jewelers you asked for the time: http://news.google.com/newspapers?nid=1499&dat=19451005&id=Sh4aAAAAIBAJ&sjid... ) and have mktime() return -1 for those times.