A galactic motionary startime chart was a type of chart that enabled one to set the dates of historical events.
In 2364, Data corrected a Tkon Empire portal when it claimed to still be in the Age of Bastu, noting that "according to the Tkon use of galactic motionary startime charts, after Bastu came Age of Cimi, Age of Xora, Age of Makto, and several others. (TNG: "The Last Outpost")