the amount to adjust the local device clock to bring it into conformance with the reference nist source clock and a roundtrip delay value provides the capability to launch a message to arrive at to reference clock at a specified time the dispersion value represents the maximum error of the local clock relative to the reference clock i e the official nist master server 46 time source 47 issues a time stamp to synchronize its master clock to the logical system clock of any registered device 42 using the service since precision measurements of offset and delay and definitive maximum error bounds are provided a receiving registered device can determine not only the time but the quality of the time as well each received time value is assigned a token of u201c 0 u201d or u201c 1 u201d with 1 being an acceptable or u201c certified u201d value and 0 being an unacceptable or u201c uncertified u201d value if the shim 34 perceives that the time quality is below a specified value a received time stamp value is assigned a token of 0 and excluded from current pseudorange calculations as well as calculations in sub process 13 until a time stamp having a token of 1 i e a u201c certified u201d time value is received and saved in memory 49 once both time values are saved 44 49 a comparison between the local device time and the nist certified time is made 51 and a determination as to which time resource is more precise made 53 given total and reliable access to a nist certified time source a nist time value will generally.