Possible timezone change in Argentina (starting in April?)
Hi, back here after 12+ years for a heads up... There is a Law proposal approved by the Cámara de Diputados (equivalent of the House) but yet to be approved in the Senate regarding Argentina's timezone. Argentina is currently in UTC-3 with no DST. The proposal establishes the Official Time for the whole country as UTC-4 (which is geographically more accurate), with a DST of UTC-3. The DST would start at 00:00 on the first April Sunday and would end at 00:00 on the first September Sunday. The Executive is authorized to modify these dates and to coordinate with other countries of MERCOSUR to apply changes on the same moment. This is just a heads up, since the Senate did not approve or modify the proposal. If this is approved and enacted before April 2026, we can assume the current status is DST and at 00:00 Sunday April 5th 2026 we would be moving the clock back to 23:00 Saturday April 4th. I'll keep you posted as this evolves, but don't hold your breath since on October 26th there are Legislative Elections (midterm), and half of the House and one third of the Senate will change. The new legislators will take office on December 10th. By the end of December the ordinary session of Congress ends; it may be extended by the Executive Branch, but there is no certainty about which bills can be discussed. References (all in Spanish): * Law proposal (official Cámara de Diputados site): https://www.hcdn.gob.ar/diputados/jcobos/proyecto.html?exp=1110-D-2024 (click on the "Ver documento original" button) * Status in the Senate: https://www.senado.gob.ar/parlamentario/comisiones/verExp/14.25/CD/PL (click on the "Texto Original" button for the signed proposal sent from the Cámara de Diputados; click on the "Trámite Legislativo" button for the process status in the Senate) * Brief article about the proposal on a reputed fact checking site: https://chequeado.com/el-explicador/cambio-de-huso-horario-en-la-argentina-q... -- Mariano Absatz - el Baby www.clueless.ar
On 16/10/2025 18:06, Mariano Absatz - el Baby wrote:
Argentina is currently in UTC-3 with no DST. The proposal establishes the Official Time for the whole country as UTC-4 (which is geographically more accurate), with a DST of UTC-3.
The DST would start at 00:00 on the first April Sunday and would end at 00:00 on the first September Sunday.
Hi. A member of the list kindly (and privately) made me notice that, being in the Southern hemisphere, DST will start in September and end in April and I wrote that wrong up here. I stand corrected. -- Mariano Absatz - el Baby www.clueless.ar
Mariano Absatz - el Baby via tz <tz@iana.org> writes:
The DST would start at 00:00 on the first April Sunday and would end at 00:00 on the first September Sunday.
This is a terrible idea. It means that 00:00:00 on the day DST starts does not exist (the clock goes from 23:59:59 to 01:00:00). This again means that software that uses a datetime with the time set to 00:00:00 to represent a date may conclude that the day DST starts does not exist. A better choice would be 02:00 so that DST starts by springing forward from 02:00 to 03:00 and ends by falling back from 02:00 to 01:00 (switching at 01:00 would make 00:00:00 on the day DST ends ambiguous). DES -- Dag-Erling Smørgrav - des@des.no
On 2025-10-24 09:55, Dag-Erling Smørgrav via tz wrote:
It means that 00:00:00 on the day DST starts does not exist (the clock goes from 23:59:59 to 01:00:00). This again means that software that uses a datetime with the time set to 00:00:00 to represent a date may conclude that the day DST starts does not exist.
Yes, but that behavior is reasonably common elsewhere, so such software should get fixed anyway. Next year a forward transition at 00:00 is scheduled for March 8 in Cuba, March 29 in the Azores and in Lebanon, April 24 in Egypt, and September 6 in Chile. It's not likely we'll convince all those governments to change their minds merely because some software developers can't get their act together. By staying in sync with most of Chile, the proposed Argentine rule has significant advantages over switching at a time other than midnight. For example, devices that are not updated past tzdb 2025b could set TZ="America/Santiago" next year, and get the correct time according to the proposed Argentine rule.
participants (3)
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Dag-Erling Smørgrav -
Mariano Absatz - el Baby -
Paul Eggert