On 2018-01-27 05:34, Clive D.W. Feather wrote:
Guy Harris said:
"Daylight Saving Time" presumably refers to turning clocks forward. No. That's not stated anywhere in ISO C - it's an assumption you've made.
What about a dictionary? Random House: daylight saving the practice of advancing standard time by one hour in the spring of each year and of setting it back by one hour in the fall in order to gain an extra period of daylight during the early evening. Collins: daylight-saving time time set usually one hour ahead of the local standard time, widely adopted in the summer to provide extra daylight in the evening. Also called (in the US) daylight time See also British Summer Time The current documentation of the tzdb interfaces agrees with these definitions (except for the restriction of the amount to 1 h in Random House). From (at least) 1993-01 until 2018c, inclusive, it says that the dst bit of tzdb indicates "summer time"; the claim "but we always meant dst to indicate non-standard time rather than summer time" is not tenable. Of course, tzdb may use the term "daylight-saving time" in their own specific meaning -- but this should be clearly stated in the documentation. And whether a change in the meaning of one common term (as opposed to, for instance, a new term and a clear-cut interface change) is a helpful upgrade path for the tzdb customers is not clear to me. Michael Deckers.