Previously it only got the answer correct to the minute. That's good enough for most transitions, but those involving local solar mean time (LMT) may have second deviations. So check the second before or after, that'll usually be the other side of the transition; if it isn't, do a further binary chop on seconds to hit the correct value. Most zones' canonical locations are only specified to the size of a city, so second precision is all anyone cares about; a few hundred metres difference in location would change that. The one exception is Europe/Amsterdam, which had its own Royal Observatory and time standard, hence had an offset known to greater precision; but the IANA DB duly approximates that, too, so we won't have data with millisecond precision even in that case, so don't try to refine beyond second. Change-Id: I20fb355f8113c32387ed8a84fbf5a41004273978 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> Reviewed-by: Konrad Kujawa <konrad.kujawa@qt.io>