Brazil has four time zones:
Most of the country is GMT/UTC minus three hours. This includes Rio, São Paulo, the South, Northeast, Brasília and half of the Amazon.
Mato Grosso, Mato Grosso do Sul and most of the Amazon are one hour behind Brasília time (GMT/UTC minus four hours).
A tiny part of Amazonas state and all of Acre are two hours behind Brasília time (GMT/UTC minus five hours).
The Fernando de Noronha archipelago is one hour ahead of Brasília time (GMT/UTC minus two hours).
Brazilian daylight-saving time runs from mid-October to mid-February, during which period clocks are advanced one hour – but only in the Southeast, South and Central West.