AM Part 1 - 3am ET
AM Part 2 - 7am ET
PM Part 1 - 11am ET
PM Part 2 - 3pm ET
PM2 Part 1 - 7pm ET
PM2 Part 2 - 11pm ET
Your world will vary based on where it falls in the processing order. For instance, one of my worlds runs almost right on the specified hour, but my other two run around 30 minutes behind on the Part 1 cycles, and around 15 minutes behind on the Part 2 cycles.