Links to the Leaving Cert and Junior Cert exam time tables for 2012 are posted in the resources section of this site.
Written exams start with Junior Cert English papers 1 and 2 and Leaving Cert paper 1 on Wednesday June 6th. So your study and revision program works backwards from then so that you have all course material covered in time.
As with last year note that certain subjects have an extra twenty minutes longer allowed than previous to that. These are the subjects deemed to have a lot of writing required to do the exams; English, Irish, Geography and History.