The parts of Brazil most popular with foreign visitors lie within the Brazilian standard time zone, three hours behind Greenwich Mean Time. The states of Amazonas, Roraima, Rondônia, Pará , Mato Grosso and Mato Grosso do Sul are a further one hour behind Brazilian standard time, while Acre is two hours behind. Fernando de Noronha and other oceanic islands are one hour ahead of Brazilian standard time.

In 1985 Brazil introduced daylight savings time. Brazilian summer time comes into effect in October and ends in early February. During this period of daylight saving time, Brazil's clocks go forward one hour in most of the south east. This when most of the Northern Hemisphere countries, such as the UK, are putting their clocks back one hour and coming off summer time. So, from March to October, when Brazil is on normal time and the UK is on its summer time, the time difference between Rio and London will be four hours. This drops to just two hours when Brazil goes on to summer time and the UK comes off.