{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"time-zone-transitions"},"result":{"entity_type":"calculator","id":"time-zone-transitions","calculator_id":"time-zone-transitions","canonical_url":"https://tttkmbb.com/time/time-zone-transitions","name":"IANA Time Zone Transition List","title":"IANA Time Zone Transitions – Offset and Daylight-Saving Changes from a Pinned tzdb Release","category":"time","category_name":"Time & Geography","tool_name":"list_time_zone_transitions","featured_mcp_tool":true,"description":"Lists every UTC-offset transition for one IANA zone and date range using pinned tzdb 2026d, including the local boundaries, offsets, abbreviations and whether the clock creates a gap or overlap.","use_when":"You need the next or historical daylight-saving/offset changes for scheduling, payroll, travel, audits or a regression test, with a specific reproducible tzdb version.","do_not_use_when":"You only need to convert one ordinary date-time, need legal advice about a jurisdiction's time law, or need changes announced after this pinned release.","agent_examples":["List every 2026 UTC-offset transition in America/New_York with local boundaries.","When does Australia/Adelaide change clocks between 2026-01-01 and 2027-01-01?","列出 Europe/London 在 2026 年的夏令时转换点、前后偏移和 IANA 数据版本。"],"inputs":[{"name":"time_zone","label":"IANA time zone","type":"string","required":true,"description":"IANA zone identifier present in tzdb 2026d.","example":"America/New_York"},{"name":"start_date","label":"Start date","type":"date","required":true,"description":"First local calendar date to inspect (1900-01-01 through 2100-12-31).","example":"2026-01-01"},{"name":"end_date","label":"End date","type":"date","required":true,"description":"Last local calendar date to inspect; ranges may not exceed 3,660 days.","example":"2026-12-31"}],"outputs":[{"name":"time_zone","label":"Requested zone","type":"string","decimals":4,"description":"Zone identifier supplied by the caller."},{"name":"resolved_zone_id","label":"Resolved zone","type":"string","decimals":4,"description":"Zone record used by the pinned data build."},{"name":"start_date","label":"Start date","type":"date","decimals":4,"description":"First local date inspected."},{"name":"end_date","label":"End date","type":"date","decimals":4,"description":"Last local date inspected."},{"name":"transition_count","label":"Transitions","type":"integer","decimals":4,"description":"Number of offset changes in the selected local-date range."},{"name":"transitions","label":"Transition records","type":"list","decimals":4,"description":"UTC instant, gap/overlap kind, local boundaries, abbreviations and offsets before/after."},{"name":"tzdb_version","label":"IANA tzdb version","type":"string","decimals":4,"description":"Pinned IANA release used for every offset and transition."},{"name":"dataset_version","label":"Dataset version","type":"string","decimals":4,"description":"Immutable Calcgrid evidence-package version."},{"name":"source_url","label":"Source release","type":"string","decimals":4,"description":"Version-specific official IANA release URL."},{"name":"source_sha256","label":"Source SHA-256","type":"string","decimals":4,"description":"SHA-256 of the downloaded official IANA tzdata release artifact."},{"name":"coverage_note","label":"Coverage","type":"string","decimals":4,"description":"Coverage and rule-change limitations for this fixed version."}],"input_schema":{"type":"object","properties":{"time_zone":{"description":"IANA zone identifier present in tzdb 2026d.","type":"string","examples":["America/New_York"]},"start_date":{"description":"First local calendar date to inspect (1900-01-01 through 2100-12-31).","type":"string","format":"date","examples":["2026-01-01"]},"end_date":{"description":"Last local calendar date to inspect; ranges may not exceed 3,660 days.","type":"string","format":"date","examples":["2026-12-31"]}},"additionalProperties":false,"required":["time_zone","start_date","end_date"],"examples":[{"time_zone":"America/New_York","start_date":"2026-01-01","end_date":"2026-12-31"}]},"output_schema":{"type":"object","properties":{"time_zone":{"description":"Zone identifier supplied by the caller.","type":"string"},"resolved_zone_id":{"description":"Zone record used by the pinned data build.","type":"string"},"start_date":{"description":"First local date inspected.","type":"string","format":"date"},"end_date":{"description":"Last local date inspected.","type":"string","format":"date"},"transition_count":{"description":"Number of offset changes in the selected local-date range.","type":"integer"},"transitions":{"description":"UTC instant, gap/overlap kind, local boundaries, abbreviations and offsets before/after.","type":"array"},"tzdb_version":{"description":"Pinned IANA release used for every offset and transition.","type":"string"},"dataset_version":{"description":"Immutable Calcgrid evidence-package version.","type":"string"},"source_url":{"description":"Version-specific official IANA release URL.","type":"string"},"source_sha256":{"description":"SHA-256 of the downloaded official IANA tzdata release artifact.","type":"string"},"coverage_note":{"description":"Coverage and rule-change limitations for this fixed version.","type":"string"}}},"formula":"select zone transition instants whose local boundary before or after lies inside [start_date, end_date]","method":"Reads the immutable transition array embedded from IANA tzdb 2026d; no live network call or Worker runtime offset lookup is involved.","sources":[{"name":"IANA Time Zone Database 2026d","url":"https://data.iana.org/time-zones/releases/tzdata2026d.tar.gz","type":"standard","retrieved_at":"2026-09-26","note":"Pinned release; SHA-256 0cb2aa8e333c3dc049badc42a0c61f21987b8cd44e107fa900bad764aacc7767. IANA describes tzdb as widely used but not legally authoritative."},{"name":"IANA tz database LICENSE","url":"https://data.iana.org/time-zones/tzdb/LICENSE","type":"license","retrieved_at":"2026-09-26","note":"The tz code and data are public domain unless the LICENSE names an exception; Calcgrid uses the data, not the three BSD-derived code files named there."},{"name":"Moment Timezone 0.6.4 data build","url":"https://www.npmjs.com/package/moment-timezone/v/0.6.4","type":"implementation","retrieved_at":"2026-09-26","note":"Pinned parser/data build reporting IANA data version 2026d; MIT licensed."}],"freshness":{"type":"static","max_age_seconds":null,"note":"Immutable IANA tzdb 2026d evidence package. Future government changes require a new version."},"examples":[{"name":"New York transitions in 2026","inputs":{"time_zone":"America/New_York","start_date":"2026-01-01","end_date":"2026-12-31"},"expected":{"transition_count":2,"transitions":[{"utc_datetime":"2026-03-08T07:00:00Z","kind":"gap","utc_offset_before":"-05:00","utc_offset_after":"-04:00"},{"utc_datetime":"2026-11-01T06:00:00Z","kind":"overlap","utc_offset_before":"-04:00","utc_offset_after":"-05:00"}],"tzdb_version":"2026d"},"url":"https://tttkmbb.com/api/v1/calculate/time-zone-transitions?time_zone=America%2FNew_York&start_date=2026-01-01&end_date=2026-12-31"}],"faq":[{"q":"Does an empty list mean the zone is invalid?","a":"No. A valid zone can have no offset changes in the requested range; transition_count will be zero."},{"q":"Can the future transitions change?","a":"Yes. Governments can change rules after tzdb 2026d; use the returned version and source fields and check the data index for updates."}],"tags":["IANA time zone transitions","DST dates","clock change","UTC offset history","tzdb version"],"related":[{"calculator_id":"local-time-resolver","reason":"Validate a wall time inside a transition gap or overlap."},{"calculator_id":"time-zone-converter","reason":"Convert a wall time between zones using the same pinned release."},{"calculator_id":"world-clock","reason":"Show one instant in several zones."}],"links":{"html":"https://tttkmbb.com/time/time-zone-transitions","markdown":"https://tttkmbb.com/time/time-zone-transitions.md","json":"https://tttkmbb.com/time/time-zone-transitions.json","api":"https://tttkmbb.com/api/v1/calculate/time-zone-transitions","schema":"https://tttkmbb.com/api/v1/calculators/time-zone-transitions","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-26"},"timestamp":"2026-09-27T00:06:55Z","next_actions":[{"tool":"list_time_zone_transitions","calculator_id":"time-zone-transitions","reason":"Run IANA Time Zone Transition List with the inputs above."}],"links":{"mcp":"https://tttkmbb.com/mcp","a2a":"https://tttkmbb.com/a2a","openapi":"https://tttkmbb.com/openapi.json","llms_txt":"https://tttkmbb.com/llms.txt","feed":"https://tttkmbb.com/feed.xml","ard":"https://tttkmbb.com/.well-known/ard.json","ai_catalog":"https://tttkmbb.com/.well-known/ai-catalog.json","agent_card":"https://tttkmbb.com/.well-known/agent-card.json","mcp_server_card":"https://tttkmbb.com/mcp/server-card","mcp_server_card_legacy":"https://tttkmbb.com/.well-known/mcp-server-card.json","ai_plugin":"https://tttkmbb.com/.well-known/ai-plugin.json","agent_capabilities":"https://tttkmbb.com/agent-capabilities.json","docs":"https://tttkmbb.com/docs/index.md","privacy":"https://tttkmbb.com/docs/privacy","terms":"https://tttkmbb.com/docs/terms","support":"https://tttkmbb.com/docs/support","china_work_calendar_data":"https://tttkmbb.com/api/v1/data/china-work-calendar/2026","uk_bank_holidays_data":"https://tttkmbb.com/api/v1/data/uk-bank-holidays","iana_tzdb_data":"https://tttkmbb.com/api/v1/data/iana-tzdb","markdown":"https://tttkmbb.com/time/time-zone-transitions.md"}}