Reference index

Glossary

Hour-of-week slot

The canonical unit: an integer 0-167. slot 0 = Monday 00:00 UTC; slot = weekdayMonday0·24 + hourUTC.

The 168 axis

The (ISO week × slot) coordinate, e.g. 2026-W29-S045 — a unique weekly bucket.

Instant

A moment on the UTC timeline, here epoch milliseconds. The slot is a function of the instant only.

Local wall time

A calendar/clock reading with no offset. A request; resolved to a UTC instant before it becomes a slot.

IANA zone

A named zone (Area/Location) carrying DST rules and historical offsets. Not the same as a fixed offset.

Spring-forward gap

A local wall time that does not exist because clocks jumped forward.

Fall-back fold

A local wall time that occurs twice because clocks fell back; two UTC instants.

Disambiguation

The declared policy for a gap or fold: earliest, latest, or reject.

Broadcast day

A local day starting at a declared cutover (default 06:00 local); 23/24/25 UTC hours across DST.

Daypart

A local hour band (e.g. primetime) mapped to a UTC slot-set per zone and week.

ISO week

ISO-8601 week (Monday start; week 1 has the first Thursday). weekYear can differ from the calendar year.

Requested vs executed

The honesty rule: a conversion echoes what was asked and what was produced; a gap/fold is reported, not hidden.

No silent rollup

Report at the requested time grain or reject; coarsening hours into a day is the buyer's operation.

tzdb vintage

The IANA tz database release; two systems on different releases can disagree near a changed transition.

Conversion methods

• Timestamp + zone → hour-of-week slotpolicy_dependent
• Slot + ISO week → UTC intervalexact
• Broadcast day (declared cutover) ⇄ slot-setpolicy_dependent
• Daypart (local band) ⇄ UTC slot-setweighted
• Instant → (ISO week × slot) keyexact
• Local date → national holiday flagapproximate

Edge-case catalogue (62)

• Half-hour offset zonesOffsets
• 45-minute offset zonesOffsets
• Sub-hour band straddle (general)Offsets
• Spring-forward gap (nonexistent local time)DST
• Fall-back fold (ambiguous local time)DST
• Partial-hour DST shiftDST
• DST transition time and date vary by zoneDST
• Reversed (Southern Hemisphere) DSTDST
• Non-DST region inside a DST countryDST
• Timezone-database vintage mismatchTime-zone database
• Political time change with short noticeTime-zone database
• Ambiguous zone abbreviations and bare offsetsTime-zone database
• An offset is not a zoneTime-zone database
• Windows vs IANA zone idsTime-zone database
• Historical offset changesTime-zone database
• Competing week-numbering systemsWeek systems
• Week-year ≠ calendar yearWeek systems
• 53-week yearsWeek systems
• Broadcast (Nielsen) calendar month and quarterWeek systems
• Slot-origin conventionWeek systems
• Broadcast-day cutover is not universalWeek systems
• Naive datetime with no zoneData quality
• Local timestamps read as UTC (or vice versa)Data quality
• Epoch and unit confusionInstants
• Clock skew and sentinel timestampsData quality
• Timestamp rounding / truncationData quality
• Leap secondsInstants
• Date-line weekday divergenceDate line
• Extreme offset span (UTC−12 … +14)Date line
• UTC canonical vs local experienceSemantics
• Event vs ingestion vs report timeSemantics
• Attribution-window timeMeasurement
• No silent temporal rollupMeasurement
• Slot-boundary dedup and double-countMeasurement
• Timezone inferred from geographyData quality
• Substitute (in-lieu) holiday daysWeek systems
• Movable and regional holidaysWeek systems
• Monotonic vs wall clockClocks
• Timestamp provenance (which time became canonical)Clocks
• Clock-accuracy metadataClocks
• Timestamp confidence intervalClocks
• NTP synchronization stateClocks
• VM snapshot rollbackClocks
• Container / live migrationClocks
• Offline capture, delayed replayClocks
• Clock-correction jumpsClocks
• Multiple clock authorities disagreeClocks
• AI-inferred timestampAI & agents
• Synthetic event timeAI & agents
• Embedding validity timeAI & agents
• Model training window (temporal leakage)AI & agents
• Prediction time vs observation timeAI & agents
• Partial ordering onlyDistributed systems
• Lamport / vector clocks (causal ≠ UTC order)Distributed systems
• Message-queue delay and reorderingDistributed systems
• Duplicate event replayDistributed systems
• Event versioning and correctionsDistributed systems
• False precisionPrecision
• Mixed-precision datasetPrecision
• Averaged timestampPrecision
• Sampling window vs instantPrecision
• Interval center vs start vs endPrecision

Chapters (18)

• Broadcast Day
• Causal Time vs Physical Time
• Cycle vs Interval
• Daypart to Slots
• DST Handling
• Holidays
• ISO Week
• Measurement Semantics
• Requested vs. Executed Time
• Resolution and Grain
• Slot to UTC Window
• The Temporal Interoperability Model
• Temporal Provenance
• The 168 Axis
• Time Uncertainty
• Timestamp to Slot
• Timezone Database
• Week Systems