An impact event of meteors on Edora is caused by an irregularity in its orbit, which occurs every 150 years. (SG1: "A Hundred Days")
On Arkhan's World, an unknown being, possibly Janus, appears in a Time Jumper, having just traveled backwards in time at least two hundred years. After landing, he carves into a stone column some of the things he saw in the future, but written in Ancient so the local population cannot read it. (SG1: "It's Good to Be King")
