According to the Internet Assigned Numbers Authority (IANA) which is the time zone name from the tz database.

News for the tz database

Release 2025b - 2025-03-22 13:40:46 -0700

Briefly:

New zone for Aysén Region in Chile which moves from -04/-03 to -03.

Changes to future timestamps

Chile's Aysén Region moves from -04/-03 to -03 year-round, joining the Magallanes Region. The region will not change its clocks on 2025-04-05 at 24:00, diverging from America/Santiago and creating a new zone America/Coyhaique. (Thanks to Yonathan Dossow.)

Model this as a change to standard offset effective 2025-03-20.

Since the goal of the change was to align the Aysen region with the Magallanes region, using the "America/Magallanes" timezone may be a valid work around. Provided that the systems in question, correctly reflect the current status of that timezone.

In this case, use "-03:00" or "UTC-3." This will eliminate any reliance on potentially problematic time zone identifiers. The most reliable and universally compatible approach is to use UTC offsets directly.