Mexico’s Chamber of Deputies was supposed to vote today on legislation abolishing DST in most of Mexico. Although the vote was delayed due to Internet problems, news coverage of the non-event led me to review our sources for DST in Mexico, and I found that tzdb considered the transitions in 1931 to be two changes to standard time, whereas it is considered to be DST in today’s news coverage, as well as in our main source, the history of Mexican local time published by the Investigation and Analysis Service of the Mexican Library of Congress. Fix this by considering the 1931 changes to be DST, not standard time. * NEWS: Mention this. * northamerica (Mexico): Add DST rules for 1931. (America/Mexico_City, America/Ojinaga, America/Chihuahua) (America/Hermosillo, America/Mazatlan, America/Bahia_Banderas): Use them. --- NEWS | 9 +++++++++ northamerica | 26 ++++++++------------------ 2 files changed, 17 insertions(+), 18 deletions(-) diff --git a/NEWS b/NEWS index 64327d0..bcdad41 100644 --- a/NEWS +++ b/NEWS @@ -1,5 +1,14 @@ News for the tz database +Unreleased, experimental changes + + Changes to past time zone abbreviations and DST flags + + The temporary advancement of clocks in central Mexico in summer + 1931 is now treated as daylight saving time, instead of as two + changes to standard time. + + Release 2022d - 2022-09-23 12:02:57 -0700 Briefly: diff --git a/northamerica b/northamerica index 13fb064..f848228 100644 --- a/northamerica +++ b/northamerica @@ -2617,6 +2617,8 @@ Zone America/Dawson -9:17:40 - LMT 1900 Aug 20 # longitude they are located at. # Rule NAME FROM TO - IN ON AT SAVE LETTER/S +Rule Mexico 1931 only - May 1 23:00 1:00 D +Rule Mexico 1931 only - Oct 1 0:00 0 S Rule Mexico 1939 only - Feb 5 0:00 1:00 D Rule Mexico 1939 only - Jun 25 0:00 0 S Rule Mexico 1940 only - Dec 9 0:00 1:00 D @@ -2667,9 +2669,7 @@ Zone America/Monterrey -6:41:16 - LMT 1921 Dec 31 23:18:44 Zone America/Mexico_City -6:36:36 - LMT 1922 Jan 1 0:23:24 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 Mexico C%sT 2001 Sep 30 2:00 -6:00 - CST 2002 Feb 20 -6:00 Mexico C%sT @@ -2680,9 +2680,7 @@ Zone America/Mexico_City -6:36:36 - LMT 1922 Jan 1 0:23:24 Zone America/Ojinaga -6:57:40 - LMT 1922 Jan 1 0:02:20 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 - CST 1996 -6:00 Mexico C%sT 1998 -6:00 - CST 1998 Apr Sun>=1 3:00 @@ -2692,9 +2690,7 @@ Zone America/Ojinaga -6:57:40 - LMT 1922 Jan 1 0:02:20 Zone America/Chihuahua -7:04:20 - LMT 1921 Dec 31 23:55:40 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 - CST 1996 -6:00 Mexico C%sT 1998 -6:00 - CST 1998 Apr Sun>=1 3:00 @@ -2703,9 +2699,7 @@ Zone America/Chihuahua -7:04:20 - LMT 1921 Dec 31 23:55:40 Zone America/Hermosillo -7:23:52 - LMT 1921 Dec 31 23:36:08 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 - CST 1942 Apr 24 -7:00 - MST 1949 Jan 14 -8:00 - PST 1970 @@ -2743,9 +2737,7 @@ Zone America/Hermosillo -7:23:52 - LMT 1921 Dec 31 23:36:08 Zone America/Mazatlan -7:05:40 - LMT 1921 Dec 31 23:54:20 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 - CST 1942 Apr 24 -7:00 - MST 1949 Jan 14 -8:00 - PST 1970 @@ -2755,9 +2747,7 @@ Zone America/Mazatlan -7:05:40 - LMT 1921 Dec 31 23:54:20 Zone America/Bahia_Banderas -7:01:00 - LMT 1921 Dec 31 23:59:00 -7:00 - MST 1927 Jun 10 23:00 -6:00 - CST 1930 Nov 15 - -7:00 - MST 1931 May 1 23:00 - -6:00 - CST 1931 Oct - -7:00 - MST 1932 Apr 1 + -7:00 Mexico M%sT 1932 Apr 1 -6:00 - CST 1942 Apr 24 -7:00 - MST 1949 Jan 14 -8:00 - PST 1970 -- 2.37.3