# list_time_zone_transitions Use this 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. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this 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. What it computes: 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. Example user requests: 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: time_zone (string); start_date (date); end_date (date). Complete JSON argument examples: {"time_zone":"America/New_York","start_date":"2026-01-01","end_date":"2026-12-31"} Outputs: time_zone, resolved_zone_id, start_date, end_date, transition_count, transitions, tzdb_version, dataset_version, source_url, source_sha256, coverage_note. Formula: select zone transition instants whose local boundary before or after lies inside [start_date, end_date] Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/time-zone-transitions with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/time/time-zone-transitions.md Agent View of the PolicyLayer registry record for `list_time_zone_transitions`. HTML page: https://policylayer.com/tools/com-tttkmbb-calcgrid/list-time-zone-transitions ## Facts - Tool: `list_time_zone_transitions` - Server: Calcgrid (`https://tttkmbb.com/mcp`) — https://policylayer.com/tools/com-tttkmbb-calcgrid.md - Homepage: https://github.com/https://tttkmbb.com/mcp - Risk category: Read (Low risk) - Registry record: grade D, identity unverified - Server auth posture: open - Server CORS policy: * - Server rate-limited: no - Parameters: 3 (3 required) - Recommended policy verdict: Allowed ## Parameters | Parameter | Type | Required | Description | | --- | --- | --- | --- | | `end_date` | string | yes | Last local calendar date to inspect; ranges may not exceed 3,660 days. | | `time_zone` | string | yes | IANA zone identifier present in tzdb 2026d. | | `start_date` | string | yes | First local calendar date to inspect (1900-01-01 through 2100-12-31). | Parameters from the server's own tool schema. ## Example call (MCP tools/call, JSON-RPC 2.0) ```json { "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "list_time_zone_transitions", "arguments": { "end_date": "", "time_zone": "", "start_date": "" } } } ``` ## Why list_time_zone_transitions is rated Low Even though list_time_zone_transitions only reads data, uncontrolled read access leaks sensitive information and racks up API costs: an agent caught in a retry loop can make thousands of calls a minute without anyone noticing. ## Use case AI agents call list_time_zone_transitions to retrieve information from Calcgrid without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere. ## Recommended policy (PolicyLayer) Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Calcgrid: ```json { "version": "1", "default": "deny", "tools": { "list_time_zone_transitions": {} } } ``` ## Other tools on Calcgrid (252) - `calculate_bazi_four_pillars` — Execute — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-bazi-four-pillars.md - `run_calculator` — Execute — https://policylayer.com/tools/com-tttkmbb-calcgrid/run-calculator.md - `calculate_ab_test_significance` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-ab-test-significance.md - `calculate_age` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-age.md - `calculate_bmi` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-bmi.md - `calculate_bmr` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-bmr.md - `calculate_circle_properties` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-circle-properties.md - `calculate_compound_interest` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-compound-interest.md - `calculate_depth_of_field` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-depth-of-field.md - `calculate_haversine_distance` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-haversine-distance.md - `calculate_kinetic_energy` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-kinetic-energy.md - `calculate_loan_payment` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-loan-payment.md - `calculate_molar_mass` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-molar-mass.md - `calculate_mortgage_payment` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-mortgage-payment.md - `calculate_percentage` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-percentage.md - `calculate_percentage_change` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-percentage-change.md - `calculate_running_pace` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-running-pace.md - `calculate_subnet` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-subnet.md - `calculate_t_test` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-t-test.md - `calculate_tdee` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/calculate-tdee.md - `cast_plum_blossom_hexagram` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/cast-plum-blossom-hexagram.md - `check_ar_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-ar-working-day.md - `check_at_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-at-working-day.md - `check_australia_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-australia-working-day.md - `check_bd_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-bd-working-day.md - `check_be_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-be-working-day.md - `check_bg_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-bg-working-day.md - `check_br_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-br-working-day.md - `check_canada_federal_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-canada-federal-working-day.md - `check_ch_working_day` — Read — https://policylayer.com/tools/com-tttkmbb-calcgrid/check-ch-working-day.md - …and 222 more: https://policylayer.com/tools/com-tttkmbb-calcgrid.md ## For agents This record is a snapshot. Live verdicts and the full registry: - Check every server in your MCP config at once: `npx -y policylayer stack` - Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md) - Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events` --- Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=com-tttkmbb-calcgrid · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/com-tttkmbb-calcgrid