Purpose and scope
What this dashboard measures
Measure clock drift, parts per million, and projected daily error.
The Clock Drift and Skew Calculator keeps Reference start, Reference end, Device start, and Device end visible beside the result so the inputs can be checked, saved, and reproduced without reconstructing the calculation later.
Instructions
How to use this calculator
Enter the values requested for the Clock Drift and Skew Calculator and replace every sample with the actual schedule, record, or system being analyzed.
- Use Reference start and Reference end to establish the starting conditions for the Clock Drift and Skew Calculator.
- Set Device start and Device end to match the actual case rather than leaving example assumptions in place.
- Run the Clock Drift and Skew Calculator with a baseline set of values, then change only one uncertain input at a time when comparing alternatives.
Calculation
Method used
Device elapsed time is compared with reference elapsed time to calculate skew, drift rate, and projected daily error.
The displayed formula makes the role of Reference start, Reference end, and Device start explicit. In the Clock Drift and Skew Calculator, keeping those inputs separate helps distinguish a changed assumption from a changed calculation rule.
Calculation method last reviewed: June 20, 2026.
Worked scenario
Example calculation
To audit your own Clock Drift and Skew Calculator result, compare Reference start and Reference end with the worked scenario. In the Clock Drift and Skew Calculator, if the direction or scale looks wrong, verify Device end before changing several inputs at once.
Interpretation
Interpreting the headline metric
The projected daily error assumes linear drift and no clock correction.
Read the headline together with the supporting metrics for Reference start, Reference end, and Device start. A plausible-looking Clock Drift and Skew Calculator result can still be unreliable when one of those values uses the wrong unit, date boundary, or local convention.
The Log Timestamp Normalizer and Sorter extends the Clock Drift and Skew Calculator by letting you normalize mixed-zone log entries to UTC and sort them chronologically.
Visual audit
Reading the supporting metrics
The Clock Drift and Skew Calculator dashboard summarizes Reference start, Reference end, Device start, and Device end in a headline and supporting measures. For the Clock Drift and Skew Calculator, read the original units beside any percentage or status label so a rounded headline does not hide a small but important shortage or overrun.
Boundaries
Important edge cases and limitations
Oscillator temperature, step corrections, leap handling, sampling error, and nonlinear drift are excluded.
If one of these exclusions applies, treat the Clock Drift and Skew Calculator output as a baseline and correct Device end or another affected input before recalculating.
Practical use
Recommended workflow
Measure over a representative interval and separate oscillator drift from NTP steps or manual adjustments.
Use the NTP Timestamp Converter alongside the Clock Drift and Skew Calculator to convert between UTC time and the NTP seconds epoch.
Input audit
Checklist for this calculation
- Confirm the source and units for Reference start and Reference end before entering them.
- Preserve Device start and Device end with any saved or shared Clock Drift and Skew Calculator result.
- For the Clock Drift and Skew Calculator, review the exclusions above for conditions that could change Device end or the calculation method.
- Recalculate the Clock Drift and Skew Calculator whenever a recorded input or real-world condition changes.
Questions
Frequently asked questions
What does positive drift mean?
The device clock accumulated more elapsed time than the reference and is running fast over the measurement.
When should the clock drift and skew calculator be recalculated?
Recalculate the clock drift and skew calculator after an entered value or excluded condition changes. Measure over a representative interval and separate oscillator drift from NTP steps or manual adjustments.
How is the clock drift and skew calculator result calculated?
Device elapsed time is compared with reference elapsed time to calculate skew, drift rate, and projected daily error. Drift = device elapsed − reference elapsed; ppm = drift ÷ reference elapsed × 1,000,000.
How can the worked example help check the clock drift and skew calculator?
A device gaining four seconds over one day runs about 46.3 parts per million fast. The projected daily error assumes linear drift and no clock correction.
Which conditions still need manual review after using the clock drift and skew calculator?
Oscillator temperature, step corrections, leap handling, sampling error, and nonlinear drift are excluded. Measure over a representative interval and separate oscillator drift from NTP steps or manual adjustments.
Which entries should be checked first when the clock drift and skew calculator result seems wrong?
Enter the values requested for the Clock Drift and Skew Calculator and replace every sample with the actual schedule, record, or system being analyzed. In the Clock Drift and Skew Calculator, begin with the values that define the anchor, duration, interval, or boundary.