The International Earth Rotation and Reference Systems Service (IERS) was created to provide the astronomical, geodetic, and geophysical communities with standards, geophysical data, earth orientation parameters, and celestial and terrestrial reference systems. After discovering the structure and history of the Service, users can discover the many Product, Technique, and Combination Centres located throughout the world. The website provides a series of bulletins, technical notes, and annual reports. Visitors can learn about the measurement of irregularities in the earth's rotation and observation techniques.