Abstract: A network is described for providing estimates of the current time. The network includes multiple computer systems each configured to provide an estimate of the current time in response to a received request. The computer systems are logically arranged to form a hierarchical structure, wherein the hierarchical structure includes multiple levels ranked with respect to one another. Each of the computer systems is assigned one of multiple levels of trust, and occupies one of the levels of the hierarchical structure dependent upon the assigned level of trust. The level of trust assigned to a given computer system is dependent upon a timekeeping dependability of the given computer system. The assigned level of trust may also be dependent upon a timekeeping security of the given computer system, where the timekeeping security is dependent upon a tamper resistance of the time clock of the given computer system. Methods for delegating a level of trust to a new computer system (i.e.