Calcgrid

Use this when you need to know what time an event scheduled in one city corresponds to in another city or in UTC on a specific date. 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 need the same instant in many zones at once (use world-clock), an epoch value (use unix-timestamp), or the elapsed time between two clock times (use time-duration). What it computes: Converts a wall-clock date and time between IANA zones using pinned tzdb 2026d. It reports both offsets, the UTC instant, date changes, the source-time status and every candidate UTC instant when the input falls in a repeated hour. Example user requests: Convert 2027-01-15 09:00 America/New_York to Australia/Adelaide and show both dates. | 把 2026-07-15 09:00 纽约时间换成阿德莱德时间。 | What UTC instant corresponds to 2026-10-04 01:45 in Australia/Adelaide? Inputs: date (date, optional); time (string); from_zone (string); to_zone (string); resolution_policy (enum, optional). Outputs: converted_date, converted_time, converted_datetime, converted_weekday, from_utc_offset, to_utc_offset, from_abbreviation, to_abbreviation, utc_datetime, day_difference [days], time_difference_hours [h], source_time_status, source_candidate_utc_datetimes, applied_resolution_policy, tzdb_version, dataset_version, source_url, source_sha256. Formula: utc = date + time − offset_from(date, time); converted = utc + offset_to(utc); time_difference_hours = (offset_to − offset_from) / 60 Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/time-zone-converter with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/time/time-zone-converter.md

Use this when the user asks to convert a numeric value between units of the same physical quantity: length, mass, temperature, area, volume, speed, time, data, energy, pressure, power, angle, fuel economy, force, frequency, density or torque. Unit symbols and common names are accepted. Do not use this for currency, live exchange rates or cross-quantity conversions that require density. Returns the converted value, detected quantity, exact factor and a conversion table.

Use this when you need the number of official mainland China working days in a 2024-2026 date range for an SLA, payroll, project or delivery estimate. 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 need only elapsed calendar days, another jurisdiction, an industry-specific settlement calendar, or dates outside 2024-2026. What it computes: Counts official mainland China working and non-working days in a date range using State Council holiday periods and weekend makeup workdays rather than a simple Monday-Friday rule. Example user requests: How many official China working days are there from 2026-09-18 through 2026-09-25, inclusive? | 计算2026年国庆节前后这段日期中实际需要上班的天数，要包含调休周末。 | Count mainland China business days between 2025-01-24 and 2025-02-10. Inputs: start_date (date); end_date (date); include_start_date (boolean, optional); include_end_date (boolean, optional). Outputs: normalized_start_date, normalized_end_date, working_days [working days], non_working_days [days], calendar_days_counted [days], adjusted_workdays_counted, holiday_dates_counted [days], source_document_ids, dataset_version, coverage_start, coverage_end. Formula: for each included date: working_days += is_working_day(date); non_working_days += not is_working_day(date) Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/china-working-days-between with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/everyday/china-working-days-between.md

Use this when you want to know how long an EV needs on a home wallbox, a public AC post or a DC fast charger to reach a target charge, or what the session costs at a given electricity price. 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 need a battery's charge time from ampere-hours and charger current (use battery-charge-time) or the driving range the added energy gives (use ev-range-efficiency); DC fast charging above about 80 % tapers strongly and takes longer than this constant-power estimate. What it computes: Estimates how long an electric vehicle takes to charge between two states of charge from its battery capacity, the charger power (capped by the onboard charger for AC charging) and the charging efficiency, plus the energy drawn from the grid and its cost. Inputs: battery_capacity_kwh (number, kWh); start_percent (number, %, optional); target_percent (number, %, optional); charger_power_kw (number, kW); max_onboard_charger_kw (number, kW, optional); charging_efficiency_percent (number, %, optional); electricity_price_per_kwh (number, per kWh, optional). Outputs: energy_added_kwh [kWh], energy_from_grid_kwh [kWh], effective_power_kw [kW], charging_time_hours [h], charging_time_text, cost, range_note. Formula: energy_added_kwh = battery_capacity_kwh × (target_percent − start_percent) / 100; energy_from_grid_kwh = energy_added_kwh / (charging_efficiency_percent / 100); effective_power_kw = min(charger_power_kw, max_onboard_charger_kw); charging_time_hours = energy_from_grid_kwh / effective_power_kw; cost = energy_from_grid_kwh × electricity_price_per_kwh Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/ev-charging-time with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/energy/ev-charging-time.md

Use this when you need someone's Chinese zodiac sign and element from a Gregorian birth date, especially for January–February births where the boundary matters, or the sign's traditional compatibility groups. 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 need a full Bazi chart with month, day and hour pillars (use bazi-four-pillars), or the Western star sign (use zodiac). What it computes: Finds the Chinese zodiac animal (生肖 shengxiao), sexagenary year (干支 ganzhi), stem element, yin/yang, nayin (纳音) and fixed element for a birth date, using either the Chinese New Year boundary or the 立春 (Lichun) boundary, plus the traditional relationship groups (六合, 三合, 六冲, 六害, 相刑) and 本命年 years. Inputs: birth_date (date); boundary (enum, optional); reference_year (integer, optional). Outputs: zodiac, zodiac_cn, year_ganzhi, year_ganzhi_pinyin, year_english, stem_element, yin_yang, nayin, animal_fixed_element, year_used, chinese_new_year_date, lichun_datetime, boundary_note, benmingnian_years, secret_friend, trine_partners, clash, harm, punishment, age_in_reference_year [years], is_benmingnian_in_reference_year, reference_year_zodiac. Formula: year_used = Gregorian year, minus 1 when birth_date is before Chinese New Year (or before 立春 with boundary = lichun); ganzhi index = (year_used − 4) mod 60; animal = branch = index mod 12; 六合 partner = (13 − b) mod 12; 三合 = b ± 4; 六冲 = b + 6; 六害 partner = (7 − b) mod 12 Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/chinese-zodiac with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/lunar/chinese-zodiac.md

Use this only after search_calculators when its input_hints do not resolve a range, enum or optional-field question. Return the full input/output schema, formula, sources, examples and limitations for one calculator. Do not call it when the search result already supplies enough input detail; call run_calculator instead. This tool only describes and does not calculate.

List the calculator categories with id, name, description and calculator count. Use it to orient before list_calculators. Does not perform calculations.

List all calculators, optionally filtered by category id (finance, health, fitness, math, geometry, statistics, conversion, physics, chemistry, everyday, food, construction, business, time, medical, engineering, weather, investing, developer, energy, photography, science, gaming, lunar, yijing). Returns calculator_id, name, description, use_when and required inputs for each. Use it to browse a whole category; use search_calculators for keyword lookup. Does not perform calculations.

Use this when you need the date or time of 立春, 清明, 夏至, 冬至 or any other solar term in a given year, or the full 24-term table. 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 the term that a specific date falls in (use lunar-calendar-converter), or you need sunrise/sunset times (use sunrise-sunset). What it computes: Lists the 24 solar terms (节气 jieqi) of a Gregorian year with their exact instants: the moments the Sun's apparent longitude reaches multiples of 15°, computed astronomically and shown in a chosen UTC offset (China Standard Time by default). Example user requests: List all 24 solar terms for 2027 in UTC+8. | 2026 年立春和冬至的准确时间是什么？ | When is Qingming this year in China Standard Time? Inputs: year (integer); utc_offset_hours (number, h, optional). Outputs: terms, lichun_date, spring_equinox, summer_solstice, autumn_equinox, winter_solstice, year_ganzhi, suishou_note, utc_offset. Formula: term instant: apparent geocentric solar longitude λ(JDE) = k·15° for k = 0 (春分) … 23 (惊蛰), solved by Newton iteration; UT = TT − ΔT; local time = UT + utc_offset_hours Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/solar-terms with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/lunar/solar-terms.md

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). 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

List every unit symbol supported by convert_units, grouped by quantity, with names. Use it when a unit symbol is rejected with UNKNOWN_UNIT. Does not convert anything.

Use this when you need to identify or describe a hexagram, convert between its number, name, trigram pair and line pattern, or find its derived hexagrams and palace position. 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 have moving lines and need the changed hexagram and reading rule (use hexagram-change), or you need to cast a hexagram from a date or numbers (use meihua-yishu). What it computes: Identifies one of the 64 hexagrams (六十四卦, liushisi gua) from its King Wen number, name, two trigrams or line digits and returns its lines, trigrams, nuclear (互卦, hugua), inverse (综卦, zonggua) and opposite (错卦, cuogua) hexagrams, its Jing Fang palace (京房八宫, Jingfang bagong) with 世/应 (shi/ying) lines, and the received judgment text (卦辞, guaci). Inputs: king_wen_number (integer, optional); name (string, optional); upper_trigram (string, optional); lower_trigram (string, optional); lines (string, optional). Outputs: number, name_cn, full_name_cn, pinyin, english, symbol, lines, lines_text, upper_trigram, lower_trigram, nuclear_hexagram, inverse_hexagram, opposite_hexagram, palace, palace_position, shi_line, ying_line, judgment_text, sequence_pair, binary_value, notes. Formula: lower trigram = lines 1–3, upper trigram = lines 4–6; nuclear = lines 2,3,4 + 3,4,5; inverse = reversed line order; opposite = each line flipped; binary_value = Σ line_i · 2^(i−1); 应 = 世 ± 3 Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/hexagram-lookup with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/yijing/hexagram-lookup.md

Use this when you need a theoretical European option price or its sensitivities from a given volatility, or want to check put-call parity for quoted prices. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this when the option is American with early exercise value, the underlying pays discrete dividends, or you need implied volatility from a market price (solve numerically instead). Informational only; not financial advice. What it computes: Prices a European call and put with the Black-Scholes-Merton formula from spot, strike, time to expiry, risk-free rate, volatility and a continuous dividend yield, and reports d1, d2 and the Greeks (delta, gamma, vega, theta, rho). Inputs: spot_price (number); strike_price (number); time_years (number, years); risk_free_rate_percent (number, % per year); volatility_percent (number, % per year); dividend_yield_percent (number, % per year, optional). Outputs: call_price, put_price, d1, d2, delta_call, delta_put, gamma, vega_per_1pct, theta_call_per_day, theta_put_per_day, rho_call_per_1pct, rho_put_per_1pct, put_call_parity_check. Formula: d1 = [ln(S/K) + (r − q + σ²/2)·T] / (σ·√T); d2 = d1 − σ·√T; C = S·e^(−qT)·N(d1) − K·e^(−rT)·N(d2); P = K·e^(−rT)·N(−d2) − S·e^(−qT)·N(−d1); Δ_call = e^(−qT)·N(d1); Γ = e^(−qT)·φ(d1)/(S·σ·√T); vega = S·e^(−qT)·φ(d1)·√T; Θ_call = −S·e^(−qT)·φ(d1)·σ/(2√T) − r·K·e^(−rT)·N(d2) + q·S·e^(−qT)·N(d1); ρ_call = K·T·e^(−rT)·N(d2), with r, q, σ as decimals Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/black-scholes with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/investing/black-scholes.md

Use this when you must safely turn a named-zone local time into an instant, validate a scheduled time around a daylight-saving transition, or preserve every possible interpretation instead of silently choosing one. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this when the input already includes a numeric UTC offset or Z, the task only needs the current clock time, or latitude/longitude must first be mapped to a zone. What it computes: Resolves a local wall-clock time with pinned IANA tzdb 2026d. Returns every valid UTC candidate for a repeated fall-back time, or the exact gap and shift-forward suggestion for a nonexistent spring-forward time. Example user requests: Resolve 2026-11-01 01:30 in America/New_York and return both UTC candidates. | Does 2026-03-08 02:30 exist in New York? Show the DST gap. | 判断 Australia/Adelaide 的 2026-10-04 02:30 是否存在，并给出时区数据版本。 Inputs: local_datetime (string); time_zone (string). Outputs: local_datetime, time_zone, resolved_zone_id, status, candidate_count, candidates, gap, related_transition, previous_transition, next_transition, tzdb_version, dataset_version, source_url, source_sha256, coverage_note. Formula: for each zone offset o: candidate_utc = local_wall_time + o; keep candidates whose active offset at candidate_utc equals o Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/local-time-resolver with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/time/local-time-resolver.md

Use this when the user needs one of Calcgrid's 535 deterministic calculators and no dedicated typed tool covers it. Call it immediately after search_calculators once calculator_id and input_hints are known; do not stop at search or schema discovery. Do not use it for trivial arithmetic, live rates or unrelated tasks. Returns typed values with units, formula, sources, freshness and timestamp; validation errors identify the field and a repair hint.

Use this when a user needs a deterministic calculation but none of the dedicated tools clearly matches and the calculator_id is unknown. Search 535 calculators from the complete task in English or Chinese, then call run_calculator with the top matching calculator_id and returned input_hints. Do not use this for trivial arithmetic, live data, writing tasks, or when a dedicated typed tool already matches. This tool only discovers; it does not calculate.

Use this when you know two of voltage, current and resistance in a DC or purely resistive circuit and need the third and the power. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this when the load is reactive (inductors or capacitors require impedance, not resistance), you want energy cost over time (use electric-power), or you need the equivalent resistance of several resistors (use resistors-series-parallel). What it computes: Solves Ohm's law V = I·R for whichever of voltage, current or resistance is omitted and reports the electrical power dissipated (P = V·I). Inputs: voltage_v (number, V, optional); current_a (number, A, optional); resistance_ohm (number, Ω, optional). Outputs: solved_for, voltage_v [V], current_a [A], current_ma [mA], resistance_ohm [Ω], power_w [W]. Formula: V = I × R; I = V / R; R = V / I; P = V × I = I² × R = V² / R Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/ohms-law with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/physics/ohms-law.md

Use this when you need the solutions of a second-degree polynomial equation, or the vertex and discriminant of a parabola y = ax² + bx + c. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this when the coefficient a is 0 (the equation is linear: x = −c / b), or you need roots of x^n = c for other powers (use nth-root). What it computes: Solves ax² + bx + c = 0 with the quadratic formula, reporting the discriminant, both roots (real, or complex conjugates written as strings), the vertex of the parabola and the sum and product of the roots. Inputs: a (number); b (number); c (number). Outputs: discriminant, nature, root1, root2, roots, vertex_x, vertex_y, sum_of_roots, product_of_roots. Formula: Δ = b² − 4ac; x = (−b ± √Δ) / (2a); for Δ < 0: x = −b/(2a) ± i·√(−Δ)/(2|a|); vertex = (−b/(2a), c − b²/(4a)) Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/quadratic-equation with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/math/quadratic-equation.md