Last year the government in Mexico eliminated the daylight saving time so different providers had to update their timezones so match this change. You can find more information here: https://newsus.cgtn.com/news/2022-11-13/Mexico-eliminates-daylight-saving-time-1eUHUADJneU/index.html Different service providers had to make an update of the tzdata's to avoid this issues. I believe an update is still required in Thunberbird to correct this since I had to change my current timezone from America/Mexico_City to America/Guatemala to avoid issues in the meetings times because they actually moved an hour.