Description
Choose earliest/latest UTC candidate or unique-only under an explicit policy; empty or unresolved evidence returns null.
An offset maps a supplied UTC coordinate to local civil coordinates by local = UTC + offset. Half-open spans include their start and exclude their end. A forward offset jump can leave local coordinates uncovered; a backward jump can give several UTC interpretations of one local value. These tools use explicit synthetic civil-second observations rather than a named-zone database.
Choose earliest/latest UTC candidate or unique-only under an explicit policy; empty or unresolved evidence returns null.
When to use this tool
Use this tool to choose earliest/latest UTC candidate or unique-only under an explicit policy; empty or unresolved evidence returns null.
How to use the tool and how it works
- Enter spansJson, local, policy using the definitions below. Serialize JSON text fields in the decoded shape shown below.
- Run the operation. Resolve input-format errors before interpreting an output.
- Read result.selected, result.candidateCount, using the stated boundary, ordering, sign and absence conventions.
Build every local-to-UTC candidate and sort by UTC, then original span index. earliest selects the first, latest the last, and unique selects only when exactly one occurrence exists; otherwise selected=null. Return candidateCount separately.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| spansJson | JSON array of {start,end,offset}: half-open UTC spans with local=UTC+offset, all in seconds. | Text, at most 8,192 UTF-16 code units; narrower grammar/range rules also apply. |
| local | Local civil-second coordinate within ±10¹². | Finite numeric value satisfying the stated comparisons. |
| policy | Exact candidate policy: earliest, latest or unique. | Text, at most 8,192 UTF-16 code units; narrower grammar/range rules also apply. |
These decoded structures show the examples inside JSON text fields. Supply their serialized JSON strings as input.
{
"spansJson": [
{
"start": 0,
"end": 10,
"offset": 0
},
{
"start": 10,
"end": 20,
"offset": 2
},
{
"start": 20,
"end": 30,
"offset": 0
}
]
}| Output field | Interpretation |
|---|---|
| result | Object containing the fields below. |
| result.selected | Candidate chosen by the explicit policy, or null if none qualifies. |
| result.candidateCount | Number of candidate occurrences, including duplicate equivalent interpretations. |
{
"input": {
"spansJson": "[{\"start\": 0, \"end\": 10, \"offset\": 0}, {\"start\": 10, \"end\": 20, \"offset\": 2}, {\"start\": 20, \"end\": 30, \"offset\": 0}]",
"local": 21,
"policy": "earliest"
},
"output": {
"result": {
"selected": {
"index": 1,
"utc": 19,
"offset": 2
},
"candidateCount": 2
}
}
}Limitations and assumptions
- Equal UTC candidates from duplicate spans still count as multiple occurrences and can make the unique policy reject selection.
- Span/transition coordinates are finite seconds within ±10¹² and offsets within ±86,400 seconds. Spans require start<end. No IANA database, calendar parsing, daylight-saving inference or leap seconds are included.
- Every declared outer field is required and unknown outer fields are rejected. Strings and JSON text have size limits, lists are bounded to 128 entries, and JSON nesting/node counts are bounded. Tighter operation-specific bounds stated above take precedence.
- Ordinary numeric outputs must be finite and within safe-integer magnitude. Exact large lengths/counts use decimal strings. Original record indexes and code-unit positions are zero-based; span ends are exclusive unless stated otherwise.
Alternative or Complementary methods
Keep all timestamps on one origin and in seconds, and retain gaps or competing observations. Use a maintained time-zone library when real dates, named zones or historical rules are required.
References
Similar or alternative tools
- Time Zone Local UTC Candidate List
Enumerate every offset-span UTC solution for a supplied local-second coordinate, retaining duplicates and overlapping evidence.
- Time Zone Local Ambiguity Classifier
Classify supplied local candidates without claiming missing evidence proves a real civil-clock gap; repeated/overlapping observations remain ambiguous.