Thanks for the heads-up. I talked about this with Tim. Proposed patch
attached. We'll need a new TZDB release soon.
I see two issues with the BC change.
Legally, 21 hours after the long-planned 2026-03-08 02:00 transition
from PST to PDT, this change introduces a new transition from PDT to
Pacific Time that alters the tm_isdst flag and likely the abbreviation
but does not alter the UT offset. A 21-hour gap between two transitions
is small, so initially I thought of modeling things with a single
transition. However, zic and zdump work fine with a 21-hour gap so the
attached proposed patch follows the letter of the law rather than
simplifying it.
No matter what abbreviation we use, there will be trouble. The obvious
abbreviation PT does not conform to the POSIX standard or to TZDB
guidelines, as it is one letter too short. The alphabetic abbreviation
least likely to break existing software is "MST", but that clashes with
the name "Pacific Time". The attached patch suggests some other
possibilities. I asked the BC government for guidance; if they do not
have a helpful suggestion I suspect "MST" will be the best of a bad lot
of alphabetic abbreviations, due to software compatibility issues. In
the meantime I installed into the development repository the proposed
patch, which uses a "-07" placeholder that also should work but is
jarring in a North American context.
Comments welcome of course.
From 8b46071fd85a7a9434d63894bac64d30362cc16d Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email protected]>
Date: Tue, 3 Mar 2026 09:50:14 -0800
Subject: [PROPOSED] Most of BC moves from PDT to Pacific Time on 03-09
* NEWS: Mention this.
* northamerica (America/Vancouver):
Switch from daylight to standard time on 2026-03-09.
For now, use the abbreviation "-07", though this will likely
change to "MST" unless the BC government gives us guidance.
* zonenow.tab (America/Vancouver): Add an entry that will likely
be removed after 2026-03-09 when BC switches to -07.
---
NEWS | 10 ++++++++++
northamerica | 29 ++++++++++++++++++++++++++++-
zonenow.tab | 3 +++
3 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index acd22280..3ed61963 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,15 @@
News for the tz database
+Unreleased, experimental changes
+
+ Changes to future timestamps
+
+ On 2026-03-09 British Columbia will go from daylight to standard
+ time, without a UT offset change. That is, its 2026-03-08 spring
+ forward will be its last foreseeable clock change, as it will move
+ to permanent -07 thereafter. (Thanks to Arthur David Olson.)
+
+
Release 2026a - 2026-03-01 22:59:49 -0800
Briefly:
diff --git a/northamerica b/northamerica
index 16b79af2..815fda14 100644
--- a/northamerica
+++ b/northamerica
@@ -1957,6 +1957,32 @@ Zone America/Edmonton -7:33:52 - LMT 1906 Sep
# https://searcharchives.vancouver.ca/daylight-saving-1918-starts-again-july-7-1941-start-d-s-sept-27-end-of-d-s-1941
# We have no further details, so omit them for now.
+# From Arthur David Olson (2026-03-02):
+# B. C. Gov News: “Adopting permanent daylight saving time: ‘Spring forward’
+# on March 8 will be the last time change, ending twice-yearly clock changes.”
+# https://news.gov.bc.ca/releases/2026AG0013-000209
+#
+# From Paul Eggert (2026-03-03):
+# The law specifies a 2026-03-08 02:00 switch from PST to PDT, then 21 hours
+# of PDT, then a 2026-03-09 switch to the new standard time Pacific Time,
+# i.e., just one clock change but two name changes separated by 21 hours.
+#
+# PT, the obvious abbreviation for Pacific Time, is one letter too short
+# to conform to TZDB’s (and POSIX’s) [-+[:alnum:]]{3,6} requirements.
+# I asked the BC government for advice, with no response yet.
+# For now, use the abbreviation -07; we can decide later what (if any)
+# conforming non-numeric abbreviation to use. Possibilities include:
+# MST - the most compatible with existing software and practice,
+# and already used in parts of BC and in Yukon
+# PDT - almost as software-friendly, but confusing because it implies
+# it is DST and is paired with PST, whereas PT is standard time
+# PST - straightforward but even more confusing,
+# and will likely break much software that assumes PST is -08
+# CPT, CPST - for Canadian Pacific (Standard) Time,
+# by analogy with AEST in Australia
+# P-T - conforming approximation to “PT”
+# PT+ - like P-T but suggesting one-hour advance over PST
+
# Rule NAME FROM TO - IN ON AT SAVE LETTER/S
Rule Vanc 1918 only - Apr 14 2:00 1:00 D
Rule Vanc 1918 only - Oct 27 2:00 0 S
@@ -1970,7 +1996,8 @@ Rule Vanc 1962 2006 - Oct lastSun 2:00 0 S
# Zone NAME STDOFF RULES FORMAT [UNTIL]
Zone America/Vancouver -8:12:28 - LMT 1884
-8:00 Vanc P%sT 1987
- -8:00 Canada P%sT
+ -8:00 Canada P%sT 2026 Mar 9
+ -7:00 - -07
Zone America/Dawson_Creek -8:00:56 - LMT 1884
-8:00 Canada P%sT 1947
-8:00 Vanc P%sT 1972 Aug 30 2:00
diff --git a/zonenow.tab b/zonenow.tab
index aa3a64f3..76465722 100644
--- a/zonenow.tab
+++ b/zonenow.tab
@@ -58,6 +58,9 @@ XX -2504-13005 Pacific/Pitcairn Pitcairn
# -08/-07 - PST/PDT (North America DST)
XX +340308-1181434 America/Los_Angeles Pacific (PST/PDT) - US & Canada; Mexico near US border
#
+# -08/-07 - PST/PDT (British Columbia DST) until 2026-03-09; then -07
+XX +4916-12307 America/Vancouver Pacific - BC (most areas)
+#
# -07 - MST
XX +332654-1120424 America/Phoenix Mountain Standard (MST) - Arizona; western Mexico; Yukon
#
--
2.51.0
