[tz] Time zone in the news
2013-11-18 00:05:37 GMT
On Nov 14, 2013 3:33 AM, "dusan pecek" <dusan.pecek <at> gmail.com> wrote:
> Hi, not sure if this is the right place but I will ask anyhow.
> I am interested in calculation of local time from lat, lon and UTC (ZULU).
> It basically means that local time in the past can be calculated.
> Does your database enable to do that.
I for one think this list is a fine place to ask that question.
The links I've seen others post in reply cover the answer, but to summarize, the zoneinfo database is necessary but not sufficient.
It documents the rules for timezone changes, including but not limited to summer time AKA "daylight savings" for regions that share a common rule. The key for lookups in this database is often of the form continent/city, e.g. I'm in America/New_York. Most rules have many keys.
But a separate database (and separate code) is needed to learn what rule covers (or contains) a given location as might be specified by latitude and longitude.
It appears the wrong date for DST start in Cuba in 2004 is in the database. It does not follow the same rules as the years before. The correct date should be Sunday 2004-03-28 00:00 ("Mar lastSun" rather than "Apr Sun>=1"). Richard Andersen (TT) (which I believe is also on this list) pointed out the difference between http://www.timeanddate.com/worldclock/timezone.html?n=99&syear=2000 and the IANA rules for Cuba, which led me to investigate. It appears I fixed this back when this was announced that year but unfortunately never reported it here. We've recorded an old granma.cu article, now long gone: http://www.granma.cu/espanol/2004/marzo/sab27/reloj.html But fortunately still available through the Wayback Machine: https://web.archive.org/web/20040402060750/http://www.granma.cu/espanol/2004/marzo/sab27/reloj.html Loosely translated to: "On Saturday, March 27 at midnight [end of day] clocks are moved ahead one hour, to begin this traditional schedule." Best regards, Steffen Thorsen - timeanddate.com
Hi, after reading http://www.squarefree.com/2006/11/01/continuous-daylight-saving-time/ I remembered that I saw similar timzones for Asia/Riyadh87 before. I am wondering why those zones exist — did Saudi Arabia really use this as clock time? Or are the different reasons? The zone files do not seem to contain this information. cheers, Derick
Article: http://news.nationalgeographic.com/news/2013/11/131101-when-does-daylight-savings-time-end-november-3-science/ Discussion: https://news.ycombinator.com/item?id=6658415 As usual, many commenters don't fully understand the complexities of DST. --Ted
I am in Washington for the 2013 Usenix LISA conference, which is at the Marriott Wardman Park Hotel. The hotel has helpfully posted signs in all the elevators reminding guests that they should turn their clocks back for "Standard Savings Time" tonight. -GAWollman