The Eighteenth Era represents a segment of time within the Garwian Unity, a nation located in the Unknown Regions. The Seventeenth Era came before it. In 19 BBY, on the planet Solitair found in the Unknown Regions, the Garwian dame Mimott presented Chiss officers Ar'alani and Mitth'raw'nuruodo with a contemporary fabric featuring an edging technique originating from the Eighteenth Era.
The flashbacks in Thrawn Ascendancy: Chaos Rising, a 2020 novel and the initial book in Star Wars: The Ascendancy Trilogy by Timothy Zahn, referenced the Eighteenth Era.