Changes at USNO in global timekeeping

Changes have taken place and new tendencies are now apparent in the practice of time keeping and time service for large geographical areas. This is due to an increased use of high-performance clocks in a variety of electronic systems. The new methods provide increased precision which is also useful in determining earth rotation parameters and other astronomical data. In the following, a brief account of these changes and methods is given as they have taken place in the Time Service of the U.S. Naval Observatory (USNO).