# Regional calendar: convert a Gregorian date

`POST https://api.astroway.info/v1/vedic/calendar/regional/date`

One Gregorian date in a regional calendar at the place. Solar calendars (tamil, malayalam, bengali): month, its number, day of the month and the era year. Lunisolar (gujarati, marathi): amanta month, the tithi at local sunrise with its paksha (Sud and Vad for Gujarati), adhika flag and the era year. Each answer carries the month's first and last civil day and the rule used.

Group: Vedic. Auth: `X-Api-Key` header. Operation ID: `vedic_calendar_regional_date`.

## Parameters

| Name | In | Required | Type | Description |
|---|---|---|---|---|
| `fields` | query | no | string | Comma-separated dotted paths, relative to `data`, to keep in the response. A path is applied to every element of an array, so `planets.name` means the name of each planet. Paths that match nothing come back in `_fields_unmatched`; a list where nothing matches at all is a 400, because an empty object would be a confident wrong answer. |
| `precision` | query | no | integer | Round every non-integer number in the response to this many decimal places. Integers are left alone, because an id is not a measurement. Ecliptic longitudes ship with fourteen decimals by default; 2 is about a tenth of an arcminute. |
| `Idempotency-Key` | header | no | string | Unique per logical operation, kept across retries. For 24 hours from the first request, a repeat with the same key, method, path, body and query string returns the stored response with `Idempotent-Replayed: true` and costs 0 credits. The same key with a different body or query string is a 409 `IDEMPOTENCY_KEY_REUSED`; a repeat while the first is still running is a 409 `IDEMPOTENCY_IN_PROGRESS`. Only 2xx responses are kept. See /idempotency/. |

## Request body

| Field | Type | Required | Description |
|---|---|---|---|
| `calendar` | "tamil" \| "malayalam" \| "bengali" \| "gujarati" \| "marathi" | yes | tamil, malayalam, bengali (solar months from the sankranti by each region's rule), gujarati (amanta, Vikram Samvat from Kartika), marathi (amanta, Shaka from Chaitra). |
| `date` | string | yes | Gregorian date, YYYY-MM-DD, local to the place. |
| `latitude` | number | yes | Latitude in decimal degrees, north positive. Between -66 and 66: further out the Sun does not rise on some days and a Hindu day has no start. |
| `longitude` | number | yes | Longitude in decimal degrees, east positive. |
| `timezone` | string | no | IANA zone name such as Asia/Kolkata, America/New_York or Europe/Kyiv, or auto (default) to look it up from the coordinates. Resolved day by day: each day is read on the offset that zone kept that day, so summer time is followed. |
| `timezoneOffset` | number | no | A fixed offset in hours instead of a zone, for the whole year. Ignored when timezone is sent. |
| `ayanamsaId` | number | no |  |
| `ayanamsa` | "fagan-bradley" \| "lahiri" \| "de-luce" \| "raman" \| "krishnamurti" \| "kp" \| "yukteshwar" \| "jn-bhasin" \| … | no | Sidereal school by name. Lahiri when omitted. Equivalent to ayanamsaId; send either. |

```json
{
  "calendar": "malayalam",
  "date": "2026-08-17",
  "latitude": 9.9312,
  "longitude": 76.2673,
  "timezone": "Asia/Kolkata"
}
```

## Responses

| Status | Meaning |
|---|---|
| 200 | Successful calculation |
| 400 | Validation error |
| 401 | Missing or invalid API key |

### Success fields, under `data`

| Field | Type | Required | Description |
|---|---|---|---|
| `calendar` | string | no |  |
| `date` | string | no |  |
| `month` | string | no |  |
| `monthNumber` | number | no |  |
| `day` | number | no |  |
| `tithi` | object | no |  |
| `adhika` | boolean | no |  |
| `year` | object | no |  |
| `year.era` | string | no |  |
| `year.number` | number | no |  |
| `year.name` | object | no |  |
| `monthStart` | string | no |  |
| `monthEnd` | string | no |  |
| `rule` | string | no |  |
| `place` | object | no |  |
| `place.latitude` | number | no |  |
| `place.longitude` | number | no |  |
| `place.timezone` | string | no |  |
| `place.timezoneOffset` | object | no |  |
| `place.ayanamsaId` | number | no |  |

## Example

```bash
curl -X POST https://api.astroway.info/v1/vedic/calendar/regional/date \
  -H "X-Api-Key: aw_live_..." \
  -H "Content-Type: application/json" \
  -d '{ "calendar": "malayalam", "date": "2026-08-17", "latitude": 9.9312, "longitude": 76.2673, "timezone": "Asia/Kolkata" }'
```

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