Midnight can move a result to another day
In a hypothetical example, a measurement taken at 11:30 p.m. in one time zone may appear as the next calendar day when stored in UTC. That is not necessarily a wrong date; it may be a different representation of the same instant.
An upload the following morning adds another distinct time.
Keep the meanings separate
| Timestamp | Possible meaning |
|---|---|
| Measurement time | When the observation occurred |
| Entry time | When someone documented it |
| Receipt time | When a system received the record |
| Update time | When the stored resource changed |
Sorting by the last update can make an old clinical event look new after a correction.
Day-level summaries need a rule
For sleep, symptoms, or activity, decide which local day owns an event that crosses midnight. Travel and daylight-saving changes need explicit handling too. A day is not always represented by exactly twenty-four local clock hours.
Preserve the original timestamp and offset when possible, alongside any normalized version. A clean-looking timeline is useful only if its time axis means what the reader thinks it means. Otherwise, apparent sequences can be artifacts of recording and conversion.
