Unnecessary faux transition in Atlantic/Canary 1980 Sep/28
Hi, I wouldn’t call this a bug, but a potential database inefficiency. I’m working on a TZ parser and using it to explore the timezone transitions as specified by the timezone database. I’m looking at the Atlantic/Canary transition on 1980 Sep 28 0:00s. At this time the timezone transitions from a permanent saving of 1:00 and abbreviation of WEST to a rule based savings specified by EU: 1980-09-27 23:59:59u = 1980-09-28 00:59:59 WEST // as specified by 0:00 1:00 WEST 1980-09-28 00:00:00u = 1980-09-28 01:00:00 WEST // as specified by 0:00 EU WE%sT I.e. there is no change in offset, savings, or abbreviation. And then an hour later EU specifies a savings and abbreviation change: 1980-09-28 00:59:59u = 1980-09-28 01:59:59 WEST 1980-09-28 01:00:00u = 1980-09-28 01:00:00 WET My observation is that this is a lot of transitions for one night. Would it not be better to delay the transition from "0:00 1:00 WEST” to "0:00 EU WE%sT” by one hour, and thus have only one transition instead of two? Here is a change that does so: diff --git a/europe b/europe index c64c41b..630c234 100644 --- a/europe +++ b/europe @@ -2922,7 +2922,7 @@ Zone Africa/Ceuta -0:21:16 - LMT 1901 Zone Atlantic/Canary -1:01:36 - LMT 1922 Mar # Las Palmas de Gran C. -1:00 - CANT 1946 Sep 30 1:00 # Canaries T 0:00 - WET 1980 Apr 6 0:00s - 0:00 1:00 WEST 1980 Sep 28 0:00s + 0:00 1:00 WEST 1980 Sep 28 1:00s 0:00 EU WE%sT # IATA SSIM (1996-09) says the Canaries switch at 2:00u, not 1:00u. # Ignore this for now, as the Canaries are part of the EU. Howard
Howard Hinnant <howard.hinnant <at> gmail.com> writes:
My observation is that this is a lot of transitions for one night. Would it not be better to delay the transition from "0:00 1:00 WEST” to "0:00 EU WE%sT” by one hour, and thus have only one transition instead of two? Here is a change that does so:
diff --git a/europe b/europe index c64c41b..630c234 100644 --- a/europe +++ b/europe <at> <at> -2922,7 +2922,7 <at> <at> Zone Africa/Ceuta -0:21:16 - LMT 1901 Zone Atlantic/Canary -1:01:36 - LMT 1922 Mar # Las Palmas de Gran C. -1:00 - CANT 1946 Sep 30 1:00 # Canaries T 0:00 - WET 1980 Apr 6 0:00s - 0:00 1:00 WEST 1980 Sep 28 0:00s + 0:00 1:00 WEST 1980 Sep 28 1:00s 0:00 EU WE%sT # IATA SSIM (1996-09) says the Canaries switch at 2:00u, not 1:00u. # Ignore this for now, as the Canaries are part of the EU.
Howard
Two lines were required for 1980 because Summer Time began one hour before the EU rules. The second 1980 line, switching to EU rules, could have been specified to be effective at any time from 1980 Apr 6 01:00u to 1980 Sep 28 01:00u; any time in that range, including 1980 Sep 28 00:00s, would indicate that Summer Time ends at 1980 Sep 28 01:00u, as specified in the EU rules. Why one hour before the end of Summer Time was originally chosen certainly is puzzling. Your suggestion to change the effective time to the time of the change, while not changing anything, does seem more logical. However, I would suggest, even though WEST @ 01:00s and 01:00u are the same time, that it would be easier on the eyes and the heart if 01:00u, the convention in the EU rules, were used.
On Jul 11, 2015, at 6:46 PM, Hank Wisniewski <hankw1@austin.rr.com> wrote:
Howard Hinnant <howard.hinnant <at> gmail.com> writes:
My observation is that this is a lot of transitions for one night. Would it not be better to delay the transition from "0:00 1:00 WEST” to "0:00 EU WE%sT” by one hour, and thus have only one transition instead of two? Here is a change that does so:
diff --git a/europe b/europe index c64c41b..630c234 100644 --- a/europe +++ b/europe <at> <at> -2922,7 +2922,7 <at> <at> Zone Africa/Ceuta -0:21:16 - LMT 1901 Zone Atlantic/Canary -1:01:36 - LMT 1922 Mar # Las Palmas de Gran C. -1:00 - CANT 1946 Sep 30 1:00 # Canaries T 0:00 - WET 1980 Apr 6 0:00s - 0:00 1:00 WEST 1980 Sep 28 0:00s + 0:00 1:00 WEST 1980 Sep 28 1:00s 0:00 EU WE%sT # IATA SSIM (1996-09) says the Canaries switch at 2:00u, not 1:00u. # Ignore this for now, as the Canaries are part of the EU.
Howard
Two lines were required for 1980 because Summer Time began one hour before the EU rules. The second 1980 line, switching to EU rules, could have been specified to be effective at any time from 1980 Apr 6 01:00u to 1980 Sep 28 01:00u; any time in that range, including 1980 Sep 28 00:00s, would indicate that Summer Time ends at 1980 Sep 28 01:00u, as specified in the EU rules. Why one hour before the end of Summer Time was originally chosen certainly is puzzling. Your suggestion to change the effective time to the time of the change, while not changing anything, does seem more logical.
However, I would suggest, even though WEST @ 01:00s and 01:00u are the same time, that it would be easier on the eyes and the heart if 01:00u, the convention in the EU rules, were used.
No objections here. I get the same list of transitions either way. Howard
participants (3)
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Hank Wisniewski -
Howard Hinnant -
Paul Eggert