Declare offset signs
Synthetic reference time is the common clock. Device A runs 90 seconds fast; B30 seconds slow. A logs event X at 12:00:20, B logs Y at 11:59:50. Offsets are exact constants for this drill; corrected time is device time minus signed offset.
| Event/device | Signed offset | Corrected time |
|---|---|---|
| X/A12:00:20 | +90 sec | 11:58:50 |
| Y/B11:59:50 | −30 sec | 12:00:20 |
Convert to the reference clock
- Fix the offset convention
- Subtract each signed offset
- Compare corrected timestamps
Unknown or changing offsets require an uncertainty range; exact order is not established by this model then.
Which event came first and by how much?
Show the worked answer
X first by 90 seconds. Raw timestamps suggest Y first, but correction reverses that order. The corrected ordering alone does not prove X caused Y.
Keep order separate from causation
| Case | Decision | Reason |
|---|---|---|
| Sort raw timestamps | Wrong order for supplied offsets | A fast/B slow |
| Sort corrected timestamps | X beforeY | Gap 90 sec |
Retain raw timestamp, device identity, offset source and corrected value. Replacing raw times would hide how the conclusion was obtained.