Some leaders in Colombia’s energy sector are advocating emergency
daylight saving time to ameliorate the likely power shortages coming to
Colombia during the upcoming Super El Niño[1]. Because Colombia gets
about ⅔ of its electrical energy from hydropower, a major drought would
hit its power hard.
Although it’s unclear what President-elect de la Espriella will do about
DST after he takes over in a few weeks, a recent news article about the
last time Columbia used emergency DST uncovered an off-by-one-day error
that I introduced to TZDB in 2006, concerning timestamps in Colombia on
May 2, 1992. I fixed the bug by installing the attached proposed patch.
[1]: https://www.theclimatebrink.com/p/the-strongest-el-nino-ever
From f33023d55021bc70b9272b6ac85f02a9a63df218 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email protected]>
Date: Fri, 17 Jul 2026 17:02:33 -0700
Subject: [PROPOSED] =?UTF-8?q?Colombia=E2=80=99s=201992=20spring-forward?=
=?UTF-8?q?=20was=20off=20by=20a=20day?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* Makefile (UNUSUAL_OK_CHARSET): Add ‘¿’.
* NEWS, southamerica (CO): The 1992-05-02 spring-forward was at
00:00, not 24:00. This fixes an error that I got from Shanks.
Ironically, I had put in the correct time in 1996-11-23 (released
in tzdata 1996m) because I guessed Shanks had got it wrong, but on
2006-03-22 (released in 2006c) when I updated from Shanks 5th
edition to Shanks & Pottenger 6th edition, I went back to what
Shanks had written, and this introduced the error.
---
Makefile | 2 +-
NEWS | 4 ++++
southamerica | 9 ++++++++-
3 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index f5a22f18..39a6798a 100644
--- a/Makefile
+++ b/Makefile
@@ -574,7 +574,7 @@ SAFE_CHAR= '[]'$(SAFE_CHARSET)'-]'
# These non-alphabetic, non-ASCII printable characters are
# used in commentary or in generated *.txt files
# and are not likely to cause confusion.
-UNUSUAL_OK_CHARSET= §«°±»½¾×–‘’“”•→−≤★⟨⟩⯪
+UNUSUAL_OK_CHARSET= §«°±»½¾¿×–‘’“”•→−≤★⟨⟩⯪
# Put this in a bracket expression to match spaces.
s = [:space:]
diff --git a/NEWS b/NEWS
index dd962b54..23ed6fda 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,10 @@ Release 2026c - 2026-07-08 10:23:58 -0700
saving time transitions, on 2026-09-20 at 02:00. This also
affects Western Sahara.
+ Changes to past timestamps
+
+ Colombia’s 1992-05-02 spring forward was at 00:00, not 24:00.
+
Changes to code
zic no longer overflows integers when processing outlandish input
diff --git a/southamerica b/southamerica
index bcd4abdf..8968dc8b 100644
--- a/southamerica
+++ b/southamerica
@@ -1472,13 +1472,20 @@ Zone Antarctica/Palmer 0 - -00 1965
# Milne gives 4:56:16.4 for Bogotá time in 1899. He writes,
# "A variation of fifteen minutes in the public clocks of Bogota is not rare."
+# From Paul Eggert (2026-07-17):
+
+# The 1992 spring forward was May 2 at 00:00. See:
+# Jiménez FA. La noche en que Colombia perdió una hora para encarar el apagón,
+# ¿se repetirá la historia en 2026? El Colombiano. 2026-06-21.
+# https://www.elcolombiano.com/negocios/colombia-perdio-una-hora-para-evitar-apagon-horario-gaviria-LF37983109
+
# From Alois Treindl (2022-11-10):
# End of time change in Colombia 1993 ... should be 6 February 24h ...
# DECRETO 267 DE 1993
# https://www.suin-juriscol.gov.co/viewDocument.asp?ruta=Decretos/1061335
# Rule NAME FROM TO - IN ON AT SAVE LETTER/S
-Rule CO 1992 only - May 3 0:00 1:00 -
+Rule CO 1992 only - May 2 0:00 1:00 -
Rule CO 1993 only - Feb 6 24:00 0 -
# Zone NAME STDOFF RULES FORMAT [UNTIL]
#STDOFF -4:56:16.4
--
2.55.0
