Brazil Daylight Saving Time 2012/2013 (which in Brazil is called horário de verão - "summer schedule" or "summer hours") starts on the third Sunday of October (Oct. 21, 2012). Brazil clocks will be set ahead one hour in the South, Southeast and Central West regions.
The time difference between the US and Brazil is smallest during the US summer, when the US is in Daylight Saving Time and Brazil is not.
When Does Brazil Daylight Saving Time 2012/2013 End?
The third Sunday in February is the closing day for Brazil Daylight Saving Time. So, 2012/2013 Brazil Daylight Saving Time will end on February 17, 2013.
However, in years when the third Sunday in February happens to be Carnival Sunday, clocks are only set back on the following Sunday. That was the case in 2012, when Carnival Sunday was on the 19th and 2011/2012 Brazil Daylight Saving Time ended on February 26, 2012.