NTPsec

time.achjoj.info

Report generated: Wed Oct 28 17:33:02 2026 UTC
Start Time: Tue Oct 27 15:09:02 2026 UTC
End Time: Wed Oct 28 17:33:02 2026 UTC
Report Period: 1.1 days

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -1.067 -1.011 -0.773 -0.143 0.741 1.267 1.571 1.514 2.278 0.471 -0.113 ms -4.942 11.79
Local Clock Frequency Offset 18.782 18.782 18.782 18.795 18.859 18.862 18.862 0.077 0.080 0.030 18.813 ppm 2.504e+08 1.578e+11

The time and frequency offsets between the ntpd calculated time and the local system clock. Showing frequency offset (red, in parts per million, scale on right) and the time offset (blue, in μs, scale on left). Quick changes in time offset will lead to larger frequency offsets.

These are fields 3 (time) and 4 (frequency) from the loopstats log file.



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 168.781 178.153 208.152 284.271 435.610 516.485 539.278 227.458 338.332 71.234 297.273 µs 42.53 179.4

The RMS Jitter of the local clock offset. In other words, how fast the local clock offset is changing.

Lower is better. An ideal system would be a horizontal line at 0μs.

RMS jitter is field 5 in the loopstats log file.



Local RMS Frequency Jitter

local stability plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Frequency Jitter 0.306 0.321 0.391 0.989 2.202 2.706 2.883 1.811 2.385 0.559 1.125 ppb 4.9 13.64

The RMS Frequency Jitter (aka wander) of the local clock's frequency. In other words, how fast the local clock changes frequency.

Lower is better. An ideal clock would be a horizontal line at 0ppm.

RMS Frequency Jitter is field 6 in the loopstats log file.



Local Clock Time Offset Histogram

local offset histogram plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Offset -1.067 -1.011 -0.773 -0.143 0.741 1.267 1.571 1.514 2.278 0.471 -0.113 ms -4.942 11.79

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats log file.



Local Temperatures

local temps plot

Local temperatures. These will be site-specific depending upon what temperature sensors you collect data from. Temperature changes affect the local clock crystal frequency and stability. The math of how temperature changes frequency is complex, and also depends on crystal aging. So there is no easy way to correct for it in software. This is the single most important component of frequency drift.

The Local Temperatures are from field 3 from the tempstats log file.



Local Frequency/Temp

local freq temps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 18.782 18.782 18.782 18.795 18.859 18.862 18.862 0.077 0.080 0.030 18.813 ppm 2.504e+08 1.578e+11
Temp /dev/sdb 30.000 30.000 30.000 30.000 30.000 30.000 30.000 0.000 0.000 0.000 30.000 °C
Temp LM0 10.000 11.000 11.000 13.000 14.000 15.000 16.000 3.000 4.000 0.985 12.774 °C
Temp LM1 10.000 10.000 11.000 12.000 14.000 15.000 15.000 3.000 5.000 1.044 12.134 °C
Temp LM2 47.000 47.000 47.000 48.000 50.000 50.000 50.000 3.000 3.000 0.766 48.382 °C
Temp LM3 17.500 17.500 18.000 19.000 20.500 20.500 20.500 2.500 3.000 0.666 19.030 °C
Temp LM4 16.500 17.500 18.000 19.000 20.500 20.500 20.500 2.500 3.000 0.702 19.056 °C

The frequency offsets and temperatures. Showing frequency offset (red, in parts per million, scale on right) and the temperatures.

These are field 4 (frequency) from the loopstats log file, and field 3 from the tempstats log file.



Local GPS

local gps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
nSats 4.000 5.000 6.000 8.000 10.000 11.000 12.000 4.000 6.000 1.265 7.790 nSat 152.9 872.3
TDOP 0.580 0.630 0.710 1.120 1.950 3.570 6.030 1.240 2.940 0.587 1.248 8.957 56.56

Local GPS. The Time Dilution of Precision (TDOP) is plotted in blue. The number of visible satellites (nSat) is plotted in red.

TDOP is field 3, and nSats is field 4, from the gpsd log file. The gpsd log file is created by the ntploggps program.

TDOP is a dimensionless error factor. Smaller numbers are better. TDOP ranges from 1 (ideal), 2 to 5 (good), to greater than 20 (poor). Some GNSS receivers report TDOP less than one which is theoretically impossible.



Server Offsets

peer offsets plot

The offset of all refclocks and servers. This can be useful to see if offset changes are happening in a single clock or all clocks together.

Clock Offset is field 5 in the peerstats log file.



Server Offset 150.254.190.51

peer offset 150.254.190.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 150.254.190.51 0.005 0.005 0.247 1.078 2.836 4.512 4.512 2.589 4.507 0.689 1.178 ms 4.76 21.01

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 153.19.250.123

peer offset 153.19.250.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 153.19.250.123 -1.164 -1.164 -1.074 -0.236 1.493 3.295 3.295 2.567 4.459 0.765 -0.175 ms -3.533 10.41

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 193.110.137.171

peer offset 193.110.137.171 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 193.110.137.171 -1.046 -1.046 -0.839 0.003 0.963 1.284 1.284 1.801 2.330 0.551 0.047 ms -3.279 7.398

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 194.146.251.100

peer offset 194.146.251.100 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.146.251.100 -1.307 -1.307 -0.967 -0.289 1.068 1.741 1.741 2.035 3.048 0.628 -0.186 ms -5.353 12.46

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 194.146.251.101

peer offset 194.146.251.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.146.251.101 -1.263 -1.263 -0.982 -0.072 0.929 1.362 1.362 1.911 2.625 0.570 -0.121 ms -5.208 12.77

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 194.29.130.252

peer offset 194.29.130.252 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 194.29.130.252 -0.727 -0.727 -0.515 0.107 1.041 5.241 5.241 1.556 5.968 0.965 0.280 ms 0.9969 10.36

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 195.187.245.55

peer offset 195.187.245.55 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 195.187.245.55 -1.443 -1.443 -1.054 -0.331 1.105 2.569 2.569 2.159 4.013 0.622 -0.295 ms -5.841 16.31

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 213.135.57.60

peer offset 213.135.57.60 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 213.135.57.60 -0.948 -0.948 -0.678 -0.004 1.064 3.281 3.281 1.742 4.229 0.718 0.103 ms -1.405 6.873

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Jitters

peer jitters plot

The RMS Jitter of all refclocks and servers. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 150.254.190.51

peer jitter 150.254.190.51 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 150.254.190.51 0.303 0.303 0.311 0.825 2.706 3.372 3.372 2.395 3.069 0.811 1.122 ms 2.276 5.483

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 153.19.250.123

peer jitter 153.19.250.123 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 153.19.250.123 0.149 0.149 0.267 0.733 2.048 2.165 2.165 1.781 2.016 0.524 0.898 ms 3.397 8.669

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 193.110.137.171

peer jitter 193.110.137.171 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 193.110.137.171 0.289 0.289 0.315 0.823 2.232 2.346 2.346 1.918 2.057 0.574 0.977 ms 3.307 8.295

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 194.146.251.100

peer jitter 194.146.251.100 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.146.251.100 0.275 0.275 0.375 1.083 2.226 2.812 2.812 1.850 2.538 0.560 1.129 ms 4.862 13.72

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 194.146.251.101

peer jitter 194.146.251.101 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.146.251.101 0.233 0.233 0.437 0.920 1.810 2.212 2.212 1.373 1.979 0.397 0.958 ms 7.983 25.09

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 194.29.130.252

peer jitter 194.29.130.252 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 194.29.130.252 0.169 0.169 0.258 0.570 3.120 3.690 3.690 2.863 3.520 0.996 1.141 ms 1.534 3.69

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 195.187.245.55

peer jitter 195.187.245.55 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 195.187.245.55 0.215 0.215 0.322 1.099 1.743 2.073 2.073 1.421 1.858 0.478 1.037 ms 5.186 12.31

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 213.135.57.60

peer jitter 213.135.57.60 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 213.135.57.60 0.230 0.230 0.442 1.298 2.612 3.276 3.276 2.171 3.046 0.723 1.347 ms 3.851 10.07

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset 18.782 18.782 18.782 18.795 18.859 18.862 18.862 0.077 0.080 0.030 18.813 ppm 2.504e+08 1.578e+11
Local Clock Time Offset -1.067 -1.011 -0.773 -0.143 0.741 1.267 1.571 1.514 2.278 0.471 -0.113 ms -4.942 11.79
Local RMS Frequency Jitter 0.306 0.321 0.391 0.989 2.202 2.706 2.883 1.811 2.385 0.559 1.125 ppb 4.9 13.64
Local RMS Time Jitter 168.781 178.153 208.152 284.271 435.610 516.485 539.278 227.458 338.332 71.234 297.273 µs 42.53 179.4
Server Jitter 150.254.190.51 0.303 0.303 0.311 0.825 2.706 3.372 3.372 2.395 3.069 0.811 1.122 ms 2.276 5.483
Server Jitter 153.19.250.123 0.149 0.149 0.267 0.733 2.048 2.165 2.165 1.781 2.016 0.524 0.898 ms 3.397 8.669
Server Jitter 193.110.137.171 0.289 0.289 0.315 0.823 2.232 2.346 2.346 1.918 2.057 0.574 0.977 ms 3.307 8.295
Server Jitter 194.146.251.100 0.275 0.275 0.375 1.083 2.226 2.812 2.812 1.850 2.538 0.560 1.129 ms 4.862 13.72
Server Jitter 194.146.251.101 0.233 0.233 0.437 0.920 1.810 2.212 2.212 1.373 1.979 0.397 0.958 ms 7.983 25.09
Server Jitter 194.29.130.252 0.169 0.169 0.258 0.570 3.120 3.690 3.690 2.863 3.520 0.996 1.141 ms 1.534 3.69
Server Jitter 195.187.245.55 0.215 0.215 0.322 1.099 1.743 2.073 2.073 1.421 1.858 0.478 1.037 ms 5.186 12.31
Server Jitter 213.135.57.60 0.230 0.230 0.442 1.298 2.612 3.276 3.276 2.171 3.046 0.723 1.347 ms 3.851 10.07
Server Offset 150.254.190.51 0.005 0.005 0.247 1.078 2.836 4.512 4.512 2.589 4.507 0.689 1.178 ms 4.76 21.01
Server Offset 153.19.250.123 -1.164 -1.164 -1.074 -0.236 1.493 3.295 3.295 2.567 4.459 0.765 -0.175 ms -3.533 10.41
Server Offset 193.110.137.171 -1.046 -1.046 -0.839 0.003 0.963 1.284 1.284 1.801 2.330 0.551 0.047 ms -3.279 7.398
Server Offset 194.146.251.100 -1.307 -1.307 -0.967 -0.289 1.068 1.741 1.741 2.035 3.048 0.628 -0.186 ms -5.353 12.46
Server Offset 194.146.251.101 -1.263 -1.263 -0.982 -0.072 0.929 1.362 1.362 1.911 2.625 0.570 -0.121 ms -5.208 12.77
Server Offset 194.29.130.252 -0.727 -0.727 -0.515 0.107 1.041 5.241 5.241 1.556 5.968 0.965 0.280 ms 0.9969 10.36
Server Offset 195.187.245.55 -1.443 -1.443 -1.054 -0.331 1.105 2.569 2.569 2.159 4.013 0.622 -0.295 ms -5.841 16.31
Server Offset 213.135.57.60 -0.948 -0.948 -0.678 -0.004 1.064 3.281 3.281 1.742 4.229 0.718 0.103 ms -1.405 6.873
TDOP 0.580 0.630 0.710 1.120 1.950 3.570 6.030 1.240 2.940 0.587 1.248 8.957 56.56
Temp /dev/sdb 30.000 30.000 30.000 30.000 30.000 30.000 30.000 0.000 0.000 0.000 30.000 °C
Temp LM0 10.000 11.000 11.000 13.000 14.000 15.000 16.000 3.000 4.000 0.985 12.774 °C
Temp LM1 10.000 10.000 11.000 12.000 14.000 15.000 15.000 3.000 5.000 1.044 12.134 °C
Temp LM2 47.000 47.000 47.000 48.000 50.000 50.000 50.000 3.000 3.000 0.766 48.382 °C
Temp LM3 17.500 17.500 18.000 19.000 20.500 20.500 20.500 2.500 3.000 0.666 19.030 °C
Temp LM4 16.500 17.500 18.000 19.000 20.500 20.500 20.500 2.500 3.000 0.702 19.056 °C
nSats 4.000 5.000 6.000 8.000 10.000 11.000 12.000 4.000 6.000 1.265 7.790 nSat 152.9 872.3
Summary as CSV file

Glossary:

frequency offset:
The difference between the ntpd calculated frequency and the local system clock frequency (usually in parts per million, ppm)
jitter, dispersion:
The short term change in a value. NTP measures Local Time Jitter, Refclock Jitter, and Server Jitter in seconds. Local Frequency Jitter is in ppm or ppb.
kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of kurtosis. A normal distribution has a kurtosis of three. NIST describes a kurtosis over three as "heavy tailed" and one under three as "light tailed".
ms, millisecond:
One thousandth of a second = 0.001 seconds, 1e-3 seconds
mu, mean:
The arithmetic mean: the sum of all the values divided by the number of values. The formula for mu is: "mu = (∑xi) / N". Where xi denotes the data points and N is the number of data points.
ns, nanosecond:
One billionth of a second, also one thousandth of a microsecond, 0.000000001 seconds and 1e-9 seconds.
percentile:
The value below which a given percentage of values fall.
ppb, parts per billion:
Ratio between two values. These following are all the same: 1 ppb, one in one billion, 1/1,000,000,000, 0.000,000,001, 1e-9 and 0.000,000,1%
ppm, parts per million:
Ratio between two values. These following are all the same: 1 ppm, one in one million, 1/1,000,000, 0.000,001, and 0.000,1%
‰, parts per thousand:
Ratio between two values. These following are all the same: 1 ‰. one in one thousand, 1/1,000, 0.001, and 0.1%
refclock:
Reference clock, a local GPS module or other local source of time.
remote clock:
Any clock reached over the network, LAN or WAN. Also called a peer or server.
time offset:
The difference between the ntpd calculated time and the local system clock's time. Also called phase offset.
σ, sigma:
Sigma denotes the standard deviation (SD) and is centered on the arithmetic mean of the data set. The SD is simply the square root of the variance of the data set. Two sigma is simply twice the standard deviation. Three sigma is three times sigma. Smaller is better.
The formula for sigma is: "σ = √[ ∑(xi-mu)^2 / N ]". Where xi denotes the data points and N is the number of data points.
skewness, Skew:
The skewness of a random variable X is the third standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of skewness. Wikipedia describes it best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
upstream clock:
Any server or reference clock used as a source of time.
µs, us, microsecond:
One millionth of a second, also one thousandth of a millisecond, 0.000,001 seconds, and 1e-6 seconds.



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