Method and apparatus for synchronizing an imprecise time clock

Abstract

A method and apparatus are provided for performing need based synchronization of a time clock maintained by a computer system. A number of computer systems are connected to a network, such as the Internet. Each computer system synchronizes its time clock by accessing a time server via the network. The time server may service a large number of client computer systems for purposes of providing accurate time of day readings and may therefore be subject to substantial loading. Accordingly, in each client system, the time clock is synchronized at least twice, and an amount of drift in the time clock is determined based on the two or more synchronizations. The synchronization interval for future synchronizations of the clock or the specific time of the next synchronization is then determined based upon the amount of drift, such that the time clock of each client computer system is synchronized only when necessary, and such that the loading on the time server is reduced. When the time clock is imprecise relative to that of the time server, the clock may be synchronized by obtaining time readings from a local precision timing routine to quantify network delays associated with accessing the server. The delays are then used to adjust the value returned by the time server to increase the accuracy of the local clock.