• Precession has been known since antiquity
• ca. 1543: The rotating Earth as part of the Copernican world system
• 1744: Nutation discovered by James Bradley
• 1765: Polar motion predicted by Leonhard Euler
• Around 1890: Observational evidence for polar motion (Friedrich Küstner, Seth Chandler)
• 1895: International Latitude Service (ILS) founded
• 1899: ILS started regular operation
• 1919: Bureau International de l'Heure (BIH) founded
• The BIH becomes responsible for the coordination of Universal Time (UT)
• 1955: Service International Rapid (SIR) established by the BIH, including its own polar motion determination
• 1962: ILS was superseded by the International Polar Motion Service (IPMS) by including independent stations
• 1980s: Project MERIT (Monitor Earth Rotation and Intercompare the Techniques of observation and analysis)
• 1986: Proposals for a new International Earth Rotation Service, prepared at a MERIT Workshop