I couldn't find the decree for the chilean DST change until today (even when it was published on November 23th on the Official Gazette, I searched for it on december 2018 with no avail)

http://www.diariooficial.interior.gob.cl/publicaciones/2018/11/23/42212/01/1498738.pdf

The only extra bit of information is that America/Punta_Arenas is confirmed to not change until 2022 

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Juan Correa Poblete
PS Labs (http://www.pslabs.cl)