It's been established that dating in Star Wars is based around massive, Galaxy changing events, such as the Battle of Yavin. Which is why we have stuff like BBY and ABY to mark the years around the flashpoint. I'm curious what other flashpoints might be used in-universe. The most obvious one I can think of is the Battle of Ruusan, which would be marked as BBR and ABR. It marked the end of the hundred year darkness and the final defeat of the Sith as a large force. Apart from these two flashpoints however, I'm at a loss. What other calendar or era dates might be considered significant enough to characterize their particular time frames?