On Friday, February 17, 2012 07:06:16 Konrad Rosenbaum wrote: > On Wednesday 15 February 2012, Stephen Kelly wrote: > > On Wednesday, February 15, 2012 21:55:54 Konrad Rosenbaum wrote: > > > The > > > > > > calculation results are almost identical. Almost. > > > > Is that enough? > > > > John Layt mentioned the existence of such a mapping too. > > It depends on how you define "enough".
My question was mostly rhetorical. > Both systems yield the same time for > the richer countries (US, central Europe, Japan) as long as you stay within > the limits of the last 30 years or so. Beyond that Olson tends to have more > accurate data on time shifts. This means that the time returned by Windows > and Olson DB can differ by one or two hours for dates further in the past > and for some countries that are "less important" for Microsoft. > > I'd actually recommend three engines: > > a) the default engine is basically what we have in Qt4 - it just knows > "local" and "UTC" - its backend uses the system functions > > b) OlsonDB would be the first advanced engine > > c) Windows could come later to have one that is identical to the default > engine for the local zone on Windows Yes, this is essentially what I proposed, except that I proposed only a) being part of Qt, and b) and c) to be outsourced - made possible by implementing the QTimeZone (nee QTimeScheme) abstract interface. > > > > *it is not always clear which time spec is standard and which one is > > > DST > > > > I'm not certain what you mean. > > The definition of time zones is unfortunately up to politicians, so it does > get fuzzy around the edges: while most countries either do not observe DST > or have standard time in (local) summer and DST in winter, there are > countries that have standard time in (local) winter and some kind of Anti- > DST in summer. At times countries do not switch off the time spec they > happen to be on for several years (e.g. during World War II several > countries remained on DST and called it War Time). Yes, but in the interface I proposed the output timezone depends on the input datetime, so the result can be as good as Olson can represent, right? Have you looked at my patch yet? Thanks, -- Stephen Kelly <[email protected]> | Software Engineer KDAB (Deutschland) GmbH & Co.KG, a KDAB Group Company www.kdab.com || Germany +49-30-521325470 || Sweden (HQ) +46-563-540090 KDAB - Qt Experts - Platform-Independent Software Solutions
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