{ "$schema": "./schema.json", "corpus": "tz-edge-cases", "version": "1.1.0", "tzdataVersion": "2026c", "generatedAt": "2026-08-23T12:53:23+00:00", "notes": "Expected values are computed against IANA tzdata 2026c. Cases with stability=frozen concern past instants and will not change. Cases with stability=volatile concern future instants and must be re-verified on each tzdata release. volatileReason=future_rules: subject to government decree. volatileReason=pre_1970_build_variance: tzdb gives no stability guarantee for pre-1970 data, and answers differ between upstream and backzone builds of the same release.", "counts": { "total": 68, "frozen": 64, "volatile": 4, "volatileByReason": { "future_rules": 2, "pre_1970_build_variance": 2 } }, "cases": [ { "id": "gap-us-eastern-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Northern-hemisphere 60-minute spring forward; 02:30 never occurs.", "input": { "localDateTime": "2024-03-10T02:30:00", "zone": "America/New_York" }, "expected": { "exists": false, "gapStart": "2024-03-10T02:00:00", "gapEnd": "2024-03-10T03:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2024-03-10T01:30:00-05:00", "shiftForward": "2024-03-10T03:30:00-04:00" } } }, { "id": "gap-uk-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "UK transitions at 01:00 local, not 02:00 — off-by-one-hour trap.", "input": { "localDateTime": "2024-03-31T01:30:00", "zone": "Europe/London" }, "expected": { "exists": false, "gapStart": "2024-03-31T01:00:00", "gapEnd": "2024-03-31T02:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2024-03-31T00:30:00+00:00", "shiftForward": "2024-03-31T02:30:00+01:00" } } }, { "id": "gap-lordhowe-30min-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Lord Howe Island shifts by 30 minutes, not 60.", "input": { "localDateTime": "2024-10-06T02:15:00", "zone": "Australia/Lord_Howe" }, "expected": { "exists": false, "gapStart": "2024-10-06T02:00:00", "gapEnd": "2024-10-06T02:30:00", "gapMinutes": 30.0, "resolutions": { "shiftBackward": "2024-10-06T01:45:00+10:30", "shiftForward": "2024-10-06T02:45:00+11:00" } } }, { "id": "gap-chatham-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Chatham transitions at 02:45 from a :45 base offset.", "input": { "localDateTime": "2024-09-29T03:00:00", "zone": "Pacific/Chatham" }, "expected": { "exists": false, "gapStart": "2024-09-29T02:45:00", "gapEnd": "2024-09-29T03:45:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2024-09-29T02:00:00+12:45", "shiftForward": "2024-09-29T04:00:00+13:45" } } }, { "id": "gap-troll-2hr-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Troll station shifts by 2 hours, producing a 2-hour gap.", "input": { "localDateTime": "2024-03-31T01:30:00", "zone": "Antarctica/Troll" }, "expected": { "exists": false, "gapStart": "2024-03-31T01:00:00", "gapEnd": "2024-03-31T03:00:00", "gapMinutes": 120.0, "resolutions": { "shiftBackward": "2024-03-30T23:30:00+00:00", "shiftForward": "2024-03-31T03:30:00+02:00" } } }, { "id": "gap-santiago-southern-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Southern hemisphere: spring forward occurs in September.", "input": { "localDateTime": "2024-09-08T00:30:00", "zone": "America/Santiago" }, "expected": { "exists": false, "gapStart": "2024-09-08T00:00:00", "gapEnd": "2024-09-08T01:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2024-09-07T23:30:00-04:00", "shiftForward": "2024-09-08T01:30:00-03:00" } } }, { "id": "gap-casablanca-ramadan-end-2024", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Morocco returns to +01:00 after Ramadan, creating a gap.", "input": { "localDateTime": "2024-04-14T02:30:00", "zone": "Africa/Casablanca" }, "expected": { "exists": false, "gapStart": "2024-04-14T02:00:00", "gapEnd": "2024-04-14T03:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2024-04-14T01:30:00+00:00", "shiftForward": "2024-04-14T03:30:00+01:00" } } }, { "id": "ambiguous-us-eastern-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "01:30 occurs twice; EDT then EST.", "input": { "localDateTime": "2024-11-03T01:30:00", "zone": "America/New_York" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-11-03T01:00:00", "ambiguityEnd": "2024-11-03T02:00:00", "first": { "instantUtc": "2024-11-03T05:30:00+00:00", "utcOffset": "-04:00", "abbreviation": "EDT", "isDst": true }, "second": { "instantUtc": "2024-11-03T06:30:00+00:00", "utcOffset": "-05:00", "abbreviation": "EST", "isDst": false } } }, { "id": "ambiguous-berlin-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "EU-wide transition at 03:00 local; 02:30 occurs twice.", "input": { "localDateTime": "2024-10-27T02:30:00", "zone": "Europe/Berlin" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-10-27T02:00:00", "ambiguityEnd": "2024-10-27T03:00:00", "first": { "instantUtc": "2024-10-27T00:30:00+00:00", "utcOffset": "+02:00", "abbreviation": "CEST", "isDst": true }, "second": { "instantUtc": "2024-10-27T01:30:00+00:00", "utcOffset": "+01:00", "abbreviation": "CET", "isDst": false } } }, { "id": "ambiguous-lordhowe-30min-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "30-minute ambiguity window rather than the usual 60.", "input": { "localDateTime": "2024-04-07T01:45:00", "zone": "Australia/Lord_Howe" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-04-07T01:30:00", "ambiguityEnd": "2024-04-07T02:00:00", "first": { "instantUtc": "2024-04-06T14:45:00+00:00", "utcOffset": "+11:00", "abbreviation": "+11", "isDst": true }, "second": { "instantUtc": "2024-04-06T15:15:00+00:00", "utcOffset": "+10:30", "abbreviation": "+1030", "isDst": false } } }, { "id": "ambiguous-auckland-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "Southern hemisphere: fall back occurs in April.", "input": { "localDateTime": "2024-04-07T02:30:00", "zone": "Pacific/Auckland" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-04-07T02:00:00", "ambiguityEnd": "2024-04-07T03:00:00", "first": { "instantUtc": "2024-04-06T13:30:00+00:00", "utcOffset": "+13:00", "abbreviation": "NZDT", "isDst": true }, "second": { "instantUtc": "2024-04-06T14:30:00+00:00", "utcOffset": "+12:00", "abbreviation": "NZST", "isDst": false } } }, { "id": "ambiguous-santiago-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "Chile transitions at 24:00, so the ambiguous window is late evening.", "input": { "localDateTime": "2024-04-06T23:30:00", "zone": "America/Santiago" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-04-06T23:00:00", "ambiguityEnd": "2024-04-07T00:00:00", "first": { "instantUtc": "2024-04-07T02:30:00+00:00", "utcOffset": "-03:00", "abbreviation": "-03", "isDst": true }, "second": { "instantUtc": "2024-04-07T03:30:00+00:00", "utcOffset": "-04:00", "abbreviation": "-04", "isDst": false } } }, { "id": "ambiguous-casablanca-ramadan-start-2024", "category": "ambiguous", "stability": "frozen", "volatileReason": null, "description": "Morocco drops to +00:00 for Ramadan — an inverted DST fall-back.", "input": { "localDateTime": "2024-03-10T02:30:00", "zone": "Africa/Casablanca" }, "expected": { "exists": true, "occurrences": 2, "ambiguityStart": "2024-03-10T02:00:00", "ambiguityEnd": "2024-03-10T03:00:00", "first": { "instantUtc": "2024-03-10T01:30:00+00:00", "utcOffset": "+01:00", "abbreviation": "+01", "isDst": false }, "second": { "instantUtc": "2024-03-10T02:30:00+00:00", "utcOffset": "+00:00", "abbreviation": "+00", "isDst": true } } }, { "id": "offset-kathmandu-0545", "category": "sub_hour_offset", "stability": "frozen", "volatileReason": null, "description": "+05:45 base offset; breaks integer-hour offset models.", "input": { "localDateTime": "2024-06-15T09:00:00", "zone": "Asia/Kathmandu" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-06-15T03:15:00+00:00", "utcOffset": "+05:45", "utcOffsetMinutes": 345.0, "abbreviation": "+0545", "isDst": false } }, { "id": "offset-kolkata-0530", "category": "sub_hour_offset", "stability": "frozen", "volatileReason": null, "description": "+05:30 base offset, no DST.", "input": { "localDateTime": "2024-06-15T09:00:00", "zone": "Asia/Kolkata" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-06-15T03:30:00+00:00", "utcOffset": "+05:30", "utcOffsetMinutes": 330.0, "abbreviation": "IST", "isDst": false } }, { "id": "offset-eucla-0845", "category": "sub_hour_offset", "stability": "frozen", "volatileReason": null, "description": "+08:45, one of the rarest offsets in use.", "input": { "localDateTime": "2024-06-15T09:00:00", "zone": "Australia/Eucla" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-06-15T00:15:00+00:00", "utcOffset": "+08:45", "utcOffsetMinutes": 525.0, "abbreviation": "+0845", "isDst": false } }, { "id": "offset-marquesas-neg0930", "category": "sub_hour_offset", "stability": "frozen", "volatileReason": null, "description": "-09:30; negative sub-hour offset, a common sign-handling bug.", "input": { "localDateTime": "2024-06-15T09:00:00", "zone": "Pacific/Marquesas" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-06-15T18:30:00+00:00", "utcOffset": "-09:30", "utcOffsetMinutes": -570.0, "abbreviation": "-0930", "isDst": false } }, { "id": "offset-monrovia-1971-neg004430", "category": "sub_hour_offset", "stability": "frozen", "volatileReason": null, "description": "Liberia kept -00:44:30 by law until January 1972: a legal offset with a seconds component. Unlike the pre-1970 LMT cases it is frozen, so a mismatch here is a real bug.", "input": { "localDateTime": "1971-06-15T12:00:00", "zone": "Africa/Monrovia" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "1971-06-15T12:44:30+00:00", "utcOffset": "-00:44:30", "utcOffsetMinutes": -44.5, "abbreviation": "MMT", "isDst": false } }, { "id": "inverted-casablanca-before-ramadan-2024", "category": "inverted_dst", "stability": "frozen", "volatileReason": null, "description": "Morocco at its normal +01:00 before Ramadan.", "input": { "localDateTime": "2024-03-01T12:00:00", "zone": "Africa/Casablanca" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-03-01T11:00:00+00:00", "utcOffset": "+01:00", "utcOffsetMinutes": 60.0, "abbreviation": "+01", "isDst": false } }, { "id": "inverted-casablanca-during-ramadan-2024", "category": "inverted_dst", "stability": "frozen", "volatileReason": null, "description": "Morocco at +00:00 during Ramadan — offset DROPS, on a lunar date.", "input": { "localDateTime": "2024-03-15T12:00:00", "zone": "Africa/Casablanca" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-03-15T12:00:00+00:00", "utcOffset": "+00:00", "utcOffsetMinutes": 0.0, "abbreviation": "+00", "isDst": true } }, { "id": "inverted-casablanca-after-ramadan-2024", "category": "inverted_dst", "stability": "frozen", "volatileReason": null, "description": "Morocco back at +01:00 after Ramadan.", "input": { "localDateTime": "2024-04-20T12:00:00", "zone": "Africa/Casablanca" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-04-20T11:00:00+00:00", "utcOffset": "+01:00", "utcOffsetMinutes": 60.0, "abbreviation": "+01", "isDst": false } }, { "id": "rulechange-tehran-2021-dst", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Iran observed DST (+04:30) in 2021.", "input": { "localDateTime": "2021-06-15T12:00:00", "zone": "Asia/Tehran" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2021-06-15T07:30:00+00:00", "utcOffset": "+04:30", "utcOffsetMinutes": 270.0, "abbreviation": "+0430", "isDst": true } }, { "id": "rulechange-tehran-2023-no-dst", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Iran abolished DST in 2022; same date is now +03:30.", "input": { "localDateTime": "2023-06-15T12:00:00", "zone": "Asia/Tehran" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2023-06-15T08:30:00+00:00", "utcOffset": "+03:30", "utcOffsetMinutes": 210.0, "abbreviation": "+0330", "isDst": false } }, { "id": "rulechange-mazatlan-2021-dst", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Mexico observed DST in 2021.", "input": { "localDateTime": "2021-06-15T12:00:00", "zone": "America/Mazatlan" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2021-06-15T18:00:00+00:00", "utcOffset": "-06:00", "utcOffsetMinutes": -360.0, "abbreviation": "MDT", "isDst": true } }, { "id": "rulechange-mazatlan-2023-no-dst", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Mexico abolished DST for most of the country in 2022.", "input": { "localDateTime": "2023-06-15T12:00:00", "zone": "America/Mazatlan" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2023-06-15T19:00:00+00:00", "utcOffset": "-07:00", "utcOffsetMinutes": -420.0, "abbreviation": "MST", "isDst": false } }, { "id": "rulechange-juarez-2023-still-dst", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Mexican border municipalities kept US DST rules after 2022.", "input": { "localDateTime": "2023-06-15T12:00:00", "zone": "America/Ciudad_Juarez" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2023-06-15T18:00:00+00:00", "utcOffset": "-06:00", "utcOffsetMinutes": -360.0, "abbreviation": "MDT", "isDst": true } }, { "id": "rulechange-istanbul-2015-winter", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "Istanbul in January 2015, still alternating: EET +02:00.", "input": { "localDateTime": "2015-01-15T12:00:00", "zone": "Europe/Istanbul" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2015-01-15T10:00:00+00:00", "utcOffset": "+02:00", "utcOffsetMinutes": 120.0, "abbreviation": "EET", "isDst": false } }, { "id": "rulechange-istanbul-2017-winter", "category": "rule_change", "stability": "frozen", "volatileReason": null, "description": "January 2017: +03:00. Abolishing DST left the clocks an hour forward of where they used to be in winter — the opposite of Iran and Mexico, which settled on their standard offset.", "input": { "localDateTime": "2017-01-15T12:00:00", "zone": "Europe/Istanbul" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2017-01-15T09:00:00+00:00", "utcOffset": "+03:00", "utcOffsetMinutes": 180.0, "abbreviation": "+03", "isDst": false } }, { "id": "skipped-apia-2011-12-30", "category": "skipped_date", "stability": "frozen", "volatileReason": null, "description": "Samoa skipped 30 Dec 2011 entirely when crossing the date line.", "input": { "localDateTime": "2011-12-30T12:00:00", "zone": "Pacific/Apia" }, "expected": { "exists": false, "gapStart": "2011-12-30T00:00:00", "gapEnd": "2011-12-31T00:00:00", "gapMinutes": 1440.0, "resolutions": { "shiftBackward": "2011-12-29T12:00:00-10:00", "shiftForward": "2011-12-31T12:00:00+14:00" } } }, { "id": "skipped-apia-before", "category": "skipped_date", "stability": "frozen", "volatileReason": null, "description": "Day before the skip: -10:00.", "input": { "localDateTime": "2011-12-29T12:00:00", "zone": "Pacific/Apia" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2011-12-29T22:00:00+00:00", "utcOffset": "-10:00", "utcOffsetMinutes": -600.0, "abbreviation": "-10", "isDst": true } }, { "id": "skipped-apia-after", "category": "skipped_date", "stability": "frozen", "volatileReason": null, "description": "Day after the skip: +14:00, a 24-hour jump.", "input": { "localDateTime": "2011-12-31T12:00:00", "zone": "Pacific/Apia" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2011-12-30T22:00:00+00:00", "utcOffset": "+14:00", "utcOffsetMinutes": 840.0, "abbreviation": "+14", "isDst": true } }, { "id": "intracountry-sydney-january", "category": "intra_country", "stability": "frozen", "volatileReason": null, "description": "Sydney observes DST in January (+11:00).", "input": { "localDateTime": "2024-01-15T12:00:00", "zone": "Australia/Sydney" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-01-15T01:00:00+00:00", "utcOffset": "+11:00", "utcOffsetMinutes": 660.0, "abbreviation": "AEDT", "isDst": true } }, { "id": "intracountry-brisbane-january", "category": "intra_country", "stability": "frozen", "volatileReason": null, "description": "Brisbane does not observe DST (+10:00) — same country, same instant.", "input": { "localDateTime": "2024-01-15T12:00:00", "zone": "Australia/Brisbane" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-01-15T02:00:00+00:00", "utcOffset": "+10:00", "utcOffsetMinutes": 600.0, "abbreviation": "AEST", "isDst": false } }, { "id": "intracountry-phoenix-july", "category": "intra_country", "stability": "frozen", "volatileReason": null, "description": "Arizona does not observe DST (-07:00).", "input": { "localDateTime": "2024-07-01T12:00:00", "zone": "America/Phoenix" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-07-01T19:00:00+00:00", "utcOffset": "-07:00", "utcOffsetMinutes": -420.0, "abbreviation": "MST", "isDst": false } }, { "id": "intracountry-denver-july", "category": "intra_country", "stability": "frozen", "volatileReason": null, "description": "Denver does (-06:00), despite sharing a nominal zone name.", "input": { "localDateTime": "2024-07-01T12:00:00", "zone": "America/Denver" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-07-01T18:00:00+00:00", "utcOffset": "-06:00", "utcOffsetMinutes": -360.0, "abbreviation": "MDT", "isDst": true } }, { "id": "lmt-amsterdam-1890", "category": "lmt", "stability": "volatile", "volatileReason": "pre_1970_build_variance", "description": "Offset is not a whole number of minutes. Also build-dependent: upstream merges pre-1970 Amsterdam into Brussels (+00:17:30 BMT), while backzone builds keep +00:19:32 AMT.", "input": { "localDateTime": "1890-06-15T12:00:00", "zone": "Europe/Amsterdam" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "1890-06-15T11:42:30+00:00", "utcOffset": "+00:17:30", "utcOffsetMinutes": 17.5, "abbreviation": "BMT", "isDst": false } }, { "id": "lmt-kolkata-1880", "category": "lmt", "stability": "volatile", "volatileReason": "pre_1970_build_variance", "description": "Madras Mean Time, +05:21:10. Agrees across common builds today, but pre-1970 data carries no stability guarantee.", "input": { "localDateTime": "1880-06-15T12:00:00", "zone": "Asia/Kolkata" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "1880-06-15T06:38:50+00:00", "utcOffset": "+05:21:10", "utcOffsetMinutes": 321.1666666666667, "abbreviation": "MMT", "isDst": false } }, { "id": "zerooffset-istanbul-2016-dst", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "Türkiye's last summer of daylight saving: +03:00, DST flag set.", "input": { "localDateTime": "2016-07-15T12:00:00", "zone": "Europe/Istanbul" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2016-07-15T09:00:00+00:00", "utcOffset": "+03:00", "utcOffsetMinutes": 180.0, "abbreviation": "EEST", "isDst": true } }, { "id": "zerooffset-istanbul-2017-permanent", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "The same +03:00 a year later, DST flag now clear and the abbreviation changed EEST to +03. The September 2016 transition moved no clocks at all.", "input": { "localDateTime": "2017-07-15T12:00:00", "zone": "Europe/Istanbul" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2017-07-15T09:00:00+00:00", "utcOffset": "+03:00", "utcOffsetMinutes": 180.0, "abbreviation": "+03", "isDst": false } }, { "id": "zerooffset-asuncion-2024-dst", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "Paraguay began daylight saving as usual in October 2024: -03:00, DST set.", "input": { "localDateTime": "2024-10-10T12:00:00", "zone": "America/Asuncion" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-10-10T15:00:00+00:00", "utcOffset": "-03:00", "utcOffsetMinutes": -180.0, "abbreviation": "-03", "isDst": true } }, { "id": "zerooffset-asuncion-2024-permanent", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "Nine days later Paraguay made that offset permanent. Same -03:00, DST flag clear, no clock movement.", "input": { "localDateTime": "2024-10-20T12:00:00", "zone": "America/Asuncion" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-10-20T15:00:00+00:00", "utcOffset": "-03:00", "utcOffsetMinutes": -180.0, "abbreviation": "-03", "isDst": false } }, { "id": "zerooffset-guam-2000-gst", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "Guam as GST, +10:00, no DST.", "input": { "localDateTime": "2000-12-01T12:00:00", "zone": "Pacific/Guam" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2000-12-01T02:00:00+00:00", "utcOffset": "+10:00", "utcOffsetMinutes": 600.0, "abbreviation": "GST", "isDst": false } }, { "id": "zerooffset-guam-2001-chst", "category": "zero_offset_transition", "stability": "frozen", "volatileReason": null, "description": "Renamed to ChST. Offset and DST flag both unchanged — the abbreviation is the only thing that moved.", "input": { "localDateTime": "2001-01-15T12:00:00", "zone": "Pacific/Guam" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2001-01-15T02:00:00+00:00", "utcOffset": "+10:00", "utcOffsetMinutes": 600.0, "abbreviation": "ChST", "isDst": false } }, { "id": "negativedst-dublin-january", "category": "negative_dst", "stability": "frozen", "volatileReason": null, "description": "Irish Standard Time is the SUMMER offset. Winter GMT is modelled as negative daylight saving, so isDst is true in January at +00:00.", "input": { "localDateTime": "2024-01-15T12:00:00", "zone": "Europe/Dublin" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-01-15T12:00:00+00:00", "utcOffset": "+00:00", "utcOffsetMinutes": 0.0, "abbreviation": "GMT", "isDst": true } }, { "id": "negativedst-dublin-july", "category": "negative_dst", "stability": "frozen", "volatileReason": null, "description": "July is +01:00 IST with isDst false — inverted relative to every other EU zone, which flag their summer offset as DST.", "input": { "localDateTime": "2024-07-15T12:00:00", "zone": "Europe/Dublin" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-07-15T11:00:00+00:00", "utcOffset": "+01:00", "utcOffsetMinutes": 60.0, "abbreviation": "IST", "isDst": false } }, { "id": "negativedst-windhoek-2016-january", "category": "negative_dst", "stability": "frozen", "volatileReason": null, "description": "Namibia before 2017: January is CAT +02:00 with isDst false.", "input": { "localDateTime": "2016-01-15T12:00:00", "zone": "Africa/Windhoek" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2016-01-15T10:00:00+00:00", "utcOffset": "+02:00", "utcOffsetMinutes": 120.0, "abbreviation": "CAT", "isDst": false } }, { "id": "negativedst-windhoek-2016-june", "category": "negative_dst", "stability": "frozen", "volatileReason": null, "description": "June is WAT +01:00 with isDst TRUE. The winter offset carries the DST flag, and 'West Africa Time' is the daylight-saving name.", "input": { "localDateTime": "2016-06-15T12:00:00", "zone": "Africa/Windhoek" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2016-06-15T11:00:00+00:00", "utcOffset": "+01:00", "utcOffsetMinutes": 60.0, "abbreviation": "WAT", "isDst": true } }, { "id": "offsetmove-almaty-2024-before", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "Kazakhstan at +06:00 before unifying its two zones.", "input": { "localDateTime": "2024-02-15T12:00:00", "zone": "Asia/Almaty" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-02-15T06:00:00+00:00", "utcOffset": "+06:00", "utcOffsetMinutes": 360.0, "abbreviation": "+06", "isDst": false } }, { "id": "offsetmove-almaty-2024-after", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "+05:00 afterwards. The transition fell on 29 February — a standard-offset change, no DST anywhere near it, on a leap day.", "input": { "localDateTime": "2024-03-15T12:00:00", "zone": "Asia/Almaty" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2024-03-15T07:00:00+00:00", "utcOffset": "+05:00", "utcOffsetMinutes": 300.0, "abbreviation": "+05", "isDst": false } }, { "id": "offsetmove-caracas-2016-before", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "Venezuela at -04:30, a sub-hour STANDARD offset.", "input": { "localDateTime": "2016-04-15T12:00:00", "zone": "America/Caracas" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2016-04-15T16:30:00+00:00", "utcOffset": "-04:30", "utcOffsetMinutes": -270.0, "abbreviation": "-0430", "isDst": false } }, { "id": "offsetmove-caracas-2016-after", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "Retired to -04:00 in May 2016. A hardcoded offset table written before then is still wrong today.", "input": { "localDateTime": "2016-06-15T12:00:00", "zone": "America/Caracas" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2016-06-15T16:00:00+00:00", "utcOffset": "-04:00", "utcOffsetMinutes": -240.0, "abbreviation": "-04", "isDst": false } }, { "id": "offsetmove-famagusta-2017-plus03", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "Northern Cyprus followed Türkiye to permanent +03:00 in 2016.", "input": { "localDateTime": "2017-01-15T12:00:00", "zone": "Asia/Famagusta" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2017-01-15T09:00:00+00:00", "utcOffset": "+03:00", "utcOffsetMinutes": 180.0, "abbreviation": "+03", "isDst": false } }, { "id": "offsetmove-famagusta-2018-reverted", "category": "offset_move", "stability": "frozen", "volatileReason": null, "description": "Then reverted to EET +02:00 in October 2017 — the same decision taken and untaken thirteen months apart, while Istanbul kept +03:00.", "input": { "localDateTime": "2018-01-15T12:00:00", "zone": "Asia/Famagusta" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2018-01-15T10:00:00+00:00", "utcOffset": "+02:00", "utcOffsetMinutes": 120.0, "abbreviation": "EET", "isDst": false } }, { "id": "gap-cairo-midnight-2023", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Egypt re-adopted DST in 2023 and transitions at midnight, so 28 April has no 00:xx hour: the local day starts at 01:00.", "input": { "localDateTime": "2023-04-28T00:30:00", "zone": "Africa/Cairo" }, "expected": { "exists": false, "gapStart": "2023-04-28T00:00:00", "gapEnd": "2023-04-28T01:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2023-04-27T23:30:00+02:00", "shiftForward": "2023-04-28T01:30:00+03:00" } } }, { "id": "gap-casey-3hour-2020", "category": "gap", "stability": "frozen", "volatileReason": null, "description": "Casey shifts by three hours, the largest routine jump in the database — larger than Troll's two.", "input": { "localDateTime": "2020-10-04T01:30:00", "zone": "Antarctica/Casey" }, "expected": { "exists": false, "gapStart": "2020-10-04T00:01:00.644531", "gapEnd": "2020-10-04T03:01:00.644531", "gapMinutes": 180.0, "resolutions": { "shiftBackward": "2020-10-03T22:30:00+08:00", "shiftForward": "2020-10-04T04:30:00+11:00" } } }, { "id": "volatile-us-eastern-2027-gap", "category": "gap", "stability": "volatile", "volatileReason": "future_rules", "description": "Correct under current US rules; would change if permanent DST passes.", "input": { "localDateTime": "2027-03-14T02:30:00", "zone": "America/New_York" }, "expected": { "exists": false, "gapStart": "2027-03-14T02:00:00", "gapEnd": "2027-03-14T03:00:00", "gapMinutes": 60.0, "resolutions": { "shiftBackward": "2027-03-14T01:30:00-05:00", "shiftForward": "2027-03-14T03:30:00-04:00" } } }, { "id": "volatile-casablanca-2027", "category": "inverted_dst", "stability": "volatile", "volatileReason": "future_rules", "description": "Depends on the projected lunar Ramadan window for 2027.", "input": { "localDateTime": "2027-06-15T12:00:00", "zone": "Africa/Casablanca" }, "expected": { "exists": true, "occurrences": 1, "instantUtc": "2027-06-15T12:00:00+00:00", "utcOffset": "+00:00", "utcOffsetMinutes": 0.0, "abbreviation": "+00", "isDst": false } }, { "id": "conv-ny-london-desync-march", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "US has sprung forward, UK has not: the gap is 4 hours, not the usual 5.", "input": { "localDateTime": "2024-03-10T09:00:00", "fromZone": "America/New_York", "toZone": "Europe/London", "fold": 0 }, "expected": { "instantUtc": "2024-03-10T13:00:00+00:00", "fromUtcOffset": "-04:00", "toUtcOffset": "+00:00", "toLocalDateTime": "2024-03-10T13:00:00", "offsetDeltaMinutes": 240.0, "dayShift": 0 } }, { "id": "conv-ny-london-desync-october", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "UK has fallen back, US has not: again 4 hours, in the other direction.", "input": { "localDateTime": "2024-10-27T09:00:00", "fromZone": "America/New_York", "toZone": "Europe/London", "fold": 0 }, "expected": { "instantUtc": "2024-10-27T13:00:00+00:00", "fromUtcOffset": "-04:00", "toUtcOffset": "+00:00", "toLocalDateTime": "2024-10-27T13:00:00", "offsetDeltaMinutes": 240.0, "dayShift": 0 } }, { "id": "conv-ny-london-normal", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Baseline: the usual 5-hour gap, for contrast with the two above.", "input": { "localDateTime": "2024-06-15T09:00:00", "fromZone": "America/New_York", "toZone": "Europe/London", "fold": 0 }, "expected": { "instantUtc": "2024-06-15T13:00:00+00:00", "fromUtcOffset": "-04:00", "toUtcOffset": "+01:00", "toLocalDateTime": "2024-06-15T14:00:00", "offsetDeltaMinutes": 300.0, "dayShift": 0 } }, { "id": "conv-ambiguous-source-fold0", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Ambiguous source time, first occurrence (EDT).", "input": { "localDateTime": "2024-11-03T01:30:00", "fromZone": "America/New_York", "toZone": "UTC", "fold": 0 }, "expected": { "instantUtc": "2024-11-03T05:30:00+00:00", "fromUtcOffset": "-04:00", "toUtcOffset": "+00:00", "toLocalDateTime": "2024-11-03T05:30:00", "offsetDeltaMinutes": 240.0, "dayShift": 0 } }, { "id": "conv-ambiguous-source-fold1", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Same wall clock, second occurrence (EST) — one hour later in UTC.", "input": { "localDateTime": "2024-11-03T01:30:00", "fromZone": "America/New_York", "toZone": "UTC", "fold": 1 }, "expected": { "instantUtc": "2024-11-03T06:30:00+00:00", "fromUtcOffset": "-05:00", "toUtcOffset": "+00:00", "toLocalDateTime": "2024-11-03T06:30:00", "offsetDeltaMinutes": 300.0, "dayShift": 0 } }, { "id": "conv-kathmandu-kolkata-15min", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Neighbouring zones 15 minutes apart (+05:45 to +05:30).", "input": { "localDateTime": "2024-06-15T09:00:00", "fromZone": "Asia/Kathmandu", "toZone": "Asia/Kolkata", "fold": 0 }, "expected": { "instantUtc": "2024-06-15T03:15:00+00:00", "fromUtcOffset": "+05:45", "toUtcOffset": "+05:30", "toLocalDateTime": "2024-06-15T08:45:00", "offsetDeltaMinutes": -15.0, "dayShift": 0 } }, { "id": "conv-kolkata-eucla-315", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Delta of 3h15m: neither endpoint nor the difference is a whole hour.", "input": { "localDateTime": "2024-06-15T09:00:00", "fromZone": "Asia/Kolkata", "toZone": "Australia/Eucla", "fold": 0 }, "expected": { "instantUtc": "2024-06-15T03:30:00+00:00", "fromUtcOffset": "+05:30", "toUtcOffset": "+08:45", "toLocalDateTime": "2024-06-15T12:15:00", "offsetDeltaMinutes": 195.0, "dayShift": 0 } }, { "id": "conv-kolkata-newyork-dayshift", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Conversion moves backwards across the date boundary.", "input": { "localDateTime": "2024-06-15T02:00:00", "fromZone": "Asia/Kolkata", "toZone": "America/New_York", "fold": 0 }, "expected": { "instantUtc": "2024-06-14T20:30:00+00:00", "fromUtcOffset": "+05:30", "toUtcOffset": "-04:00", "toLocalDateTime": "2024-06-14T16:30:00", "offsetDeltaMinutes": -570.0, "dayShift": -1 } }, { "id": "conv-apia-la-datechange", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Near the date line: same instant, previous calendar day at the target.", "input": { "localDateTime": "2024-06-15T10:00:00", "fromZone": "Pacific/Apia", "toZone": "America/Los_Angeles", "fold": 0 }, "expected": { "instantUtc": "2024-06-14T21:00:00+00:00", "fromUtcOffset": "+13:00", "toUtcOffset": "-07:00", "toLocalDateTime": "2024-06-14T14:00:00", "offsetDeltaMinutes": -1200.0, "dayShift": -1 } }, { "id": "conv-kiritimati-midway-25h", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "+14:00 to -11:00: the widest spread in use, 25 hours, landing on the previous calendar day.", "input": { "localDateTime": "2024-06-15T10:00:00", "fromZone": "Pacific/Kiritimati", "toZone": "Pacific/Midway", "fold": 0 }, "expected": { "instantUtc": "2024-06-14T20:00:00+00:00", "fromUtcOffset": "+14:00", "toUtcOffset": "-11:00", "toLocalDateTime": "2024-06-14T09:00:00", "offsetDeltaMinutes": -1500.0, "dayShift": -1 } }, { "id": "conv-istanbul-athens-divergence", "category": "conversion", "stability": "frozen", "volatileReason": null, "description": "Istanbul and Athens shared EET/EEST until September 2016. Afterwards they differ by an hour in winter and not at all in summer.", "input": { "localDateTime": "2017-01-15T12:00:00", "fromZone": "Europe/Istanbul", "toZone": "Europe/Athens", "fold": 0 }, "expected": { "instantUtc": "2017-01-15T09:00:00+00:00", "fromUtcOffset": "+03:00", "toUtcOffset": "+02:00", "toLocalDateTime": "2017-01-15T11:00:00", "offsetDeltaMinutes": -60.0, "dayShift": 0 } } ] }