The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Parameter (EOP) and International Celestial Reference System (ICRS) groups.

The IERS has various components located in the United States, Europe and Australia.

Part of its mission involves the determination of a time scale based on the current rate of the rotation of the Earth.

The definitions and relationships among ITRF, ICRF and EOP are established by IERS conventions standards.

[1] A mission of the IERS is to provide earth orientation information to the greater geodesy community in the form of bulletins:[2][3]