NIST - UTC(NIST)


Grid 1 Day Averages 1 Hour Averages 10 Minute Averages Next Date Last Date    

ServerNISTIP Address132.163.96.2 LocationBoulder, ColoradoDate2021-04-23 (MJD 59327) Period1 day

Method Hours Time Offset (ms) Range (ms) Frequency Offset Confidence (r) Round Trip Delay (ms)
AVG 24.00 0.3114 8.555 -9.11 x 10-10 -0.04 1.834
MIN 24.00 0.2585 0.081 +3.82 x 10-10 +0.35 1.083




Allan Deviation (ADEV)
Averaging Time ()
(hours, minutes)		 Samples ADEV
(AVG Method)		 ADEV
(MIN Method)
0 h, 10 min 141 1.49 x 10-6 3.77 x 10-8
0 h, 20 min 139 8.06 x 10-7 2.08 x 10-8
0 h, 40 min 135 4.03 x 10-7 1.04 x 10-8
1 h, 20 min 127 2.00 x 10-7 5.51 x 10-9
2 h, 40 min 111 9.17 x 10-8 2.48 x 10-9
5 h, 20 min 79 2.14 x 10-8 9.57 x 10-10


Time Deviation (TDEV)
Averaging Time ()
(hours, minutes)		 Samples TDEV
(AVG Method), ms		 TDEV
(MIN Method), ms
0 h, 10 min 141 0.5145 0.0131
0 h, 20 min 138 0.4064 0.0109
0 h, 40 min 132 0.3100 0.0086
1 h, 20 min 120 0.2367 0.0056
2 h, 40 min 96 0.1134 0.0041
5 h, 20 min 48 0.0422 0.0056


Legend
AVG MethodThe AVG method involves comparing each NTP server to UTC(NIST) every 10 seconds, and then averaging these measurements for 10 minutes (60 readings). UTC(NIST) is available with 0.0001 ms resolution. The difference between the two 10-minute averages is the difference between the time broadcast by the server and UTC(NIST).
MIN MethodThe MIN method involves comparing each NTP server to UTC(NIST) every 10 seconds for a 10 minute interval (60 measurements). However, only one of the 60 measurements is saved, the one with the shortest round trip delay. This method saves only 1.67% of the measurements, and is based on the assumption that NTP measurements with the shortest round trip delays provide the best estimate of the true time difference. UTC(NIST) is available with 0.0001 ms resolution. The time difference between the server and UTC(NIST) is obtained by subtracting the two time readings obtained from the measurement with the smallest round trip delay.
HoursThe duration of the comparision in hours.
Time OffsetThe average time offset obtained during the entire comparison, expressed in milliseconds.
RangeThe difference between the maximum and minimum time offset values, expressed in milliseconds.
Frequency OffsetThe average frequency offset betweeen the NTP server and UTC(NIST). This estimate is obtained by fitting a least squares line to all of the recorded data and then applying the equation: delta-t/T, where delta-t is estimated from the slope of the least squares line.
Confidence Level (r)The confidence level of the estimated frequency offset. The confidence level is the correlation coefficient (r) of the least squares line fitted to the data.
Round Trip DelayThe average round trip delay for the AVG and MIN methods, expressed in milliseconds. The round trip delay generally increases as a function of the distance between the server and NIST. It also increases during periods when the network or server traffic is using a high percentage of the available bandwidth.
Time DeviationThe time deviation (TDEV) of the collected data at various intervals, expressed in milliseconds. TDEV is a metric used to estimate time stability.
Allan DeviationThe Allan deviation (ADEV) of the collected data at various intervals, expressed as a dimensionless value. ADEV is a metric used to estimate frequency stability.