From 0252f09cdff3769ecbf6adfdaf6c47055bbfb74b Mon Sep 17 00:00:00 2001 From: Tim Parenti Date: Sat, 20 Feb 2021 16:57:44 -0500 Subject: Fix Guyana LMT and later historical transitions (Thanks to P Chan.) * NEWS: Mention this. * southamerica (America/Guyana): Move LMT 1 second east to match the offset given by the Official Gazette of British Guiana in 1915. Standard time of -04 was observed for a few years bginning on 1911-08-01 before the transition to -0345 on 1915-03-01. Better clarify the 1975 transition and our guessed 1991 transition (actually in 1992) from sources. --- NEWS | 8 +++++++- southamerica | 37 +++++++++++++++++++++++++++++++++---- 2 files changed, 40 insertions(+), 5 deletions(-) diff --git a/NEWS b/NEWS index f3c94ed..b7d37f2 100644 --- a/NEWS +++ b/NEWS @@ -4,7 +4,13 @@ Unreleased, experimental changes Changes to past timestamps - Portugal observed DST in 1950. (Thanks to Alois Treindl.) + Correct many pre-1993 transitions, fixing entries originally + derived from Shanks and from Whitman. The fixes include: + - Guyana: corrected LMT for Georgetown; the introduction of + standard time in 1911, not 1915; and corrections to 1975 and + 1992 transitions + - Portugal: DST was observed in 1950 + (Thanks to Alois Treindl and P Chan.) Changes to code diff --git a/southamerica b/southamerica index aad8b2d..beb3052 100644 --- a/southamerica +++ b/southamerica @@ -1540,11 +1540,40 @@ Zone America/Cayenne -3:29:20 - LMT 1911 Jul -3:00 - -03 # Guyana + +# From P Chan (2020-11-27): +# https://books.google.com/books?id=5-5CAQAAMAAJ&pg=SA1-PA547 +# The Official Gazette of British Guiana. (New Series.) Vol. XL. July to +# December, 1915, p 1547, lists as several notes: +# "Local Mean Time 3 hours 52 mins. 39 secs. slow of Greenwich Mean Time +# (Georgetown.) From 1st August, 1911, British Guiana Standard Mean Time 4 +# hours slow of Greenwich Mean Time, by notice in Official Gazette on 1st July, +# 1911. From 1st March, 1915, British Guiana Standard Mean Time 3 hours 45 +# mins. 0 secs. slow of Greenwich Mean Time, by notice in Official Gazette on +# 23rd January, 1915." +# +# https://parliament.gov.gy/documents/acts/10923-act_no._27_of_1975_-_interpretation_and_general_clauses_(amendment)_act_1975.pdf +# Interpretation and general clauses (Amendment) Act 1975 (Act No. 27 of 1975) +# [dated 1975-07-31] +# "This Act...shall come into operation on 1st August, 1975." +# "...where any expression of time occurs...the time referred to shall signify +# the standard time of Guyana which shall be three hours behind Greenwich Mean +# Time." +# +# Circular No. 10/1992 dated 1992-03-20 +# https://dps.gov.gy/wp-content/uploads/2018/12/1992-03-20-Circular-010.pdf +# "...cabinet has decided that with effect from Sunday 29th March, 1992, Guyana +# Standard Time would be re-established at 01:00 hours by adjusting the hands +# of the clock back to 24:00 hours." +# Legislated in the Interpretation and general clauses (Amendment) Act 1992 +# (Act No. 6 of 1992) [passed 1992-03-27, published 1992-04-18] +# https://parliament.gov.gy/documents/acts/5885-6_of_1992_interpretation_and_general_clauses_(amendment)_act_1992.pdf + # Zone NAME STDOFF RULES FORMAT [UNTIL] -Zone America/Guyana -3:52:40 - LMT 1915 Mar # Georgetown - -3:45 - -0345 1975 Jul 31 - -3:00 - -03 1991 -# IATA SSIM (1996-06) says -4:00. Assume a 1991 switch. +Zone America/Guyana -3:52:39 - LMT 1911 Aug 1 # Georgetown + -4:00 - -04 1915 Mar 1 + -3:45 - -0345 1975 Aug 1 + -3:00 - -03 1992 Mar 29 1:00 -4:00 - -04 # Paraguay -- 2.15.1