---
title: "Forecast Calendar"
method: POST
path: "/forecast-calendar"
tags: ["Prognostics"]
---

# Forecast Calendar

`POST /forecast-calendar`

Generate a combined forecast calendar including transits, lunar phases, ingresses, and retrograde stations for a given period.

## Request body

- ForecastCalendar — Wrapper { natal: ChartInput } used by endpoints that take a base natal plus extra parameters in flat fields.
  - `natal` ChartInput, required — Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC. city is a display label only: nothing here geocodes it, so it never stands in for coordinates.
    - `date` string, required
    - `time` string, required
    - `timezoneOffset` number, nullable — Hours from UTC at the given moment, not minutes. Fractional zones are hours too: 5.5 for India, 5.75 for Nepal, -3.5 for Newfoundland. Defaults to 0, meaning UTC.
    - `latitude` number, required
    - `longitude` number, required
    - `houseSystem` string
    - `name` string
    - `city` string
    - `zodiacType` 'tropical' | 'sidereal'
    - `ayanamsaId` number, nullable
    - `ayanamsa` 'fagan-bradley' | 'lahiri' | 'de-luce' | 'raman' | 'krishnamurti' | 'kp' | 'yukteshwar' | 'jn-bhasin' | 'true-citra' | 'djwhal-khul' — Sidereal school by name. Lahiri when omitted. Equivalent to ayanamsaId; send either.
    - `cosmogram` boolean
  - `year` number, nullable, required

## Response `200`

Successful calculation

- object
  - `ok` boolean
  - `data` object
    - `cells` array[], nullable
      - object[], nullable
        - `house` number, nullable
        - `month` number, nullable
        - `harmonious` number, nullable
        - `tense` number, nullable
        - `neutral` number, nullable
        - `total` number, nullable
        - `events` unknown[], nullable
          - unknown
    - `dailySummary` object[], nullable
      - `date` string, nullable
      - `jd` number, nullable
      - `harmonious` number, nullable
      - `tense` number, nullable
      - `total` number, nullable
    - `maxAbsTotal` number, nullable
    - `year` number, nullable

## Other responses

- `400` — Validation error
- `401` — Missing or invalid API key

## Changes

- **2026-08-24** `8ab5a768b521` — 1 warning, 4 info
  - removed the optional property `data/events` from the response with the `200` status
  - added the optional property `data/cells` to the response with the `200` status
  - added the optional property `data/dailySummary` to the response with the `200` status
  - added the optional property `data/maxAbsTotal` to the response with the `200` status
  - …1 more
- **2026-08-18** `dd3764875e7a` — 1 info
  - added the new optional request property `allOf[#/components/schemas/NatalWrapper]/natal/ayanamsa`
- **2026-08-15** `e637d1a9911b` — 2 warning
  - the `allOf[#/components/schemas/NatalWrapper]/natal/timezoneOffset` request property's max was set to `14.00`
  - the `allOf[#/components/schemas/NatalWrapper]/natal/timezoneOffset` request property's min was set to `-14.00`
- **2026-08-11** `b0533bcc12c0` — 4 breaking, 4 warning, 2 info
  - the request property `allOf[#/components/schemas/NatalWrapper]/natal/latitude` became not nullable
  - the request property `allOf[#/components/schemas/NatalWrapper]/natal/longitude` became not nullable
  - the request property `allOf[#/components/schemas/NatalWrapper]/natal/latitude` became required
  - the request property `allOf[#/components/schemas/NatalWrapper]/natal/longitude` became required
  - …6 more

[Change history](https://skmtc.dev/astroway/apis/astroway-calculation-api/changes/forecast-calendar/post.md)

---

[API](https://skmtc.dev/astroway/apis/astroway-calculation-api.md) · [All operations](https://skmtc.dev/astroway/apis/astroway-calculation-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/astroway/astroway-calculation-api/revisions/8ab5a768b521/schema)