Ossus Day
although not officially recognized as a holiday, this date was set aside by the Old Republic as a time for reflection and remembrance, after the planet Ossus was destroyed during the Great Sith War. Ossus Day was not observed on a regular basis, at least in terms of the Coruscant calendar. Instead, it was observed based on the seasonal time at which both of Ossus' moons aligned themselves with respect to a pair of obelisks that were once found in the city of Knossa.