Write both local and UTC boundaries
RFC 3339 timestamps represent instants with UTC offsets; a business-day interval is a separate policy. This example defines 10 October 2026 in Hong Kong as start-inclusive, end-exclusive. It does not convert a date-only field into a timestamp.
| Boundary or event | UTC representation | Included in 10 October? |
|---|---|---|
| Start: 2026-10-10T00:00:00+08:00 | 2026-10-09T16:00:00Z | Yes |
| Last whole-second example | 2026-10-10T15:59:59Z | Yes; higher precision also follows the interval |
| End: 2026-10-11T00:00:00+08:00 | 2026-10-10T16:00:00Z | No; next day starts here |
Test adjacent windows together
timestamp >= start_utc AND timestamp < end_utcKeep the zone and cutoff policy beside the export. Test an event exactly at each boundary and one with fractional seconds. Do not use “23:59:59” as an inclusive end if the source can represent finer precision.
Which day owns 2026-10-10T16:00:00Z under this rule?
Show the worked answer
11 October in Hong Kong. It is excluded from the 10 October interval and included at the start of the next interval.