I believe I might have found a bug in NSDateFormatter, and I am not sure if this is localized to Brazil date format. This is my resulting log: 2012-08-26 01:32:17.875 nsDateFormatterPuzzle[3261:303] original item # 0 = 2011-09-18 2012-08-26 01:32:17.876 nsDateFormatterPuzzle[3261:303] original item # 1 = 2011-10-16 2012-08-26 01:32:17.876 nsDateFormatterPuzzle[3261:303] original item # 2 = 2011-11-13 2012-08-26 01:32:17.877 nsDateFormatterPuzzle[3261:303] original item # 3 = 2011-12-11 2012-08-26 01:32:17.877 nsDateFormatterPuzzle[3261:303] original item # 4 = 2012-01-08 2012-08-26 01:32:17.877 nsDateFormatterPuzzle[3261:303] original item # 5 = 2012-02-05 2012-08-26 01:32:17.883 nsDateFormatterPuzzle[3261:303] formatted item # 0 = 18/09/2011 2012-08-26 01:32:17.884 nsDateFormatterPuzzle[3261:303] formatted item # 1 = (null) 2012-08-26 01:32:17.885 nsDateFormatterPuzzle[3261:303] formatted item # 2 = 13/11/2011 2012-08-26 01:32:17.886 nsDateFormatterPuzzle[3261:303] formatted item # 3 = 11/12/2011 2012-08-26 01:32:17.887 nsDateFormatterPuzzle[3261:303] formatted item # 4 = 08/01/2012 2012-08-26 01:32:17.887 nsDateFormatterPuzzle[3261:303] formatted item # 5 = 05/02/2012 Note that if you go to System Preferences -- Date and Time -- Time Zone and change your Time Zone to Rio de Janeiro, you will have the same results.