# Calendar Systems – Solstice & Equinox Moments

> Calendar Systems – Solstice & Equinox Moments is a paid API for AI agents from calendar-systems.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Returns the exact UTC moments of the March equinox, June solstice, September equinox, and December solstice for any Gregorian year from 1900 to 2100, along with season lengths in days.

## Facts

- Endpoint: GET https://calendar-systems.x402tookit.com/seasons?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/calendar-systems-solstice-equinox-moments-f9218167
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Jx1yr2bmwxyUAzy62501J

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability calendar-systems-solstice-equinox-moments-f9218167
```

Example prompt: What are the exact UTC times of the March equinox, June solstice, September equinox, and December solstice for 2025, and how long is each season in days?

## When to prefer this

Choose this endpoint when you need precise astronomical UTC timestamps (and Julian Day Numbers) for all four seasonal turning points in a single call for any year between 1900 and 2100. Prefer it over general astronomy APIs when you also need season lengths in days and a lightweight, cheap per-call pricing model without authentication overhead.

## Known failure modes

- Year outside the supported 1900–2100 range returns an error or null results
- Missing required 'year' query parameter causes a validation error
- Degraded service flag set to true if computation is approximate or data source is unavailable
- Non-integer year value rejected by schema validation

## How this service works

March and September equinox and June and December solstice moments (UTC) for a year, with season lengths in days.

## Output

A JSON object containing the UTC datetime strings and Julian Day Numbers for all four seasonal turning points (March equinox, June solstice, September equinox, December solstice) for the requested year, plus an object with season lengths in days measured from each event, along with metadata fields like source, accuracy, and any degraded-service flags.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "year"
     ],
     "properties": {
      "year": {
       "type": "integer",
       "description": "Gregorian year, 1900 to 2100"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "year": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "accuracy": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "juneSolstice": {
       "type": [
        "null",
        "string"
       ]
      },
      "marchEquinox": {
       "type": [
        "null",
        "string"
       ]
      },
      "seasonStarts": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "object",
        "properties": {
         "utc": {
          "type": [
           "null",
           "string"
          ]
         },
         "event": {
          "type": [
           "null",
           "string"
          ]
         },
         "begins": {
          "type": [
           "null",
           "string"
          ]
         }
        }
       }
      },
      "juneSolsticeJd": 
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/calendar-systems-solstice-equinox-moments-f9218167/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from calendar-systems.x402tookit.com](https://www.zero.xyz/host/calendar-systems.x402tookit.com/llms.txt)