Recovering the time of day¶
The release shifts every case to start at 2100-01-01 00:00 UTC, removing the date and the time of day. The time of day (Korean local time) can be recovered to the minute from the admission date and the seconds of the EMR times.
| Date | 2026-10-12 |
| Status | current |
| Methods | Clinical and laboratory times |
| Clocks | Recorder PC clock, Hospital records clock |
| Devices | Vital Recorder, Clinical records |
| Variables | Anaesthesia record events, Admission and discharge |
Background¶
The recorder writes Unix time (UTC). The release then shifts each case so its start reads 2100-01-01 00:00 UTC. Local Korean time (KST, UTC+9, no daylight saving since 1988) enters through the hospital systems: admission and discharge are local dates, and the EMR times are local clock times relative to the case start.
Data¶
All 6,388 rows of clinical_data.csv: the admission date (adm) and the four EMR times (anestart, opstart, aneend, opend). A clock was recovered for 6,385 cases: all four EMR times share one seconds phase in 5,774 and three of four in 611. Three cases get none (adm not on a whole minute in two, EMR times disagree in one). No waveform data were needed.
Method¶
The admission date is a local midnight expressed relative to the case start, so −adm modulo one day gives the case start's time of day; the seconds of the EMR times refine it. The case clock is accepted to the minute where three or more EMR times agree.
Results¶
- Time of day to the minute in cases where at least three EMR times agree (vitaldb_bench.case_clock).
- The case clock is KST; subtracting 9 h returns to UTC.
- It reveals which EMR entries fall on 5-minute marks, the basis of Anaesthesia record times are rounded up.
Discussion¶
One assumption cannot be tested in the release: that the recorder PC's time zone was set correctly, so its Unix time was true UTC rather than local time read as UTC. The EMR clock's own offset from the recorder cannot be separated from documentation lag (Closing loops in the timing graph).
Observations it supports¶
| Observation | Status | Summary |
|---|---|---|
| Every case starts at 2100-01-01 00:00 UTC | established | The release shifts each case to the same start, removing the date and the time of day. Within a case all times keep their spacing. |
Open questions¶
- The recorder PC's time zone (untestable assumption). Whether its Unix time was true UTC, or local time read as UTC, cannot be tested in the release.
- The PC-to-UTC link (untestable assumption). Every route from a device clock to UTC passes through the recorder PC's clock, which is assumed to have been kept on UTC by network time. The release holds no second, independent clock against which to test it, so this link is assumed, not measured.