Q: February 17: iCal glitch

I'm trying to add an event to my iCal (on my MacBook) on Feb 17, 2013 but when I double-click the date, it creates an event the day before (Feb 16). In addition, one event from a subscription calendar (Brazilian Holidays), which should be on the 17th, shows up on the 16th on my MacBook.

This date works fine on my iPhone, but if I add an event there to Feb 17, it also shows on the 16th on my MacBook.

Any ideas?

William.