You are here: Home / USNO / Earth Orientation / EO Information Center / General Information / IERS Conventions 1996 (Technical Note 21)
The USNO websites,,,,,, and are undergoing modernization efforts. The expected completion of the work and the estimated return of service is Fall 2020, subject to change due to potential impacts of COVID-19.

IERS Conventions 1996 (Technical Note 21)

The following are the chapters, subroutines, and associated information from the 1996 IERS Conventions (Technical Note 21).

USNO Master Clock Time
Javascript must be Enabled