# Market Calendar API – Index Rebalancing & Reconstitution Dates

> Market Calendar API – Index Rebalancing & Reconstitution Dates is a paid API for AI agents from market-calendar-api.onrender.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Returns scheduled index rebalancing and reconstitution dates for S&P 500, Nasdaq-100, Russell US, and DAX for a given year, including effective-after-close date and first trading day with new weights.

## Facts

- Endpoint: GET https://market-calendar-api.onrender.com/v1/rebalance?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/market-calendar-api-index-rebalancing-reconstitution-dates-ba7da847
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_T_iNlB30Wnb6Uo2UJPzt8

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 market-calendar-api-index-rebalancing-reconstitution-dates-ba7da847
```

Example prompt: What are all the index rebalancing and reconstitution dates for 2025 across S&P 500, Nasdaq-100, Russell, and DAX — including the effective-after-close date and the first trading day with new weights for each?

## When to prefer this

Choose this endpoint when you need structured, machine-readable rebalancing and reconstitution calendars for major equity indices (S&P 500, Nasdaq-100, Russell US, DAX) by year. Ideal for quantitative strategies, portfolio rebalancing automation, event-driven trading preparation, or building financial calendars that need to track when index compositions and weights change.

## Known failure modes

- Invalid or unsupported year returns an error or empty result
- Unknown index string (e.g. typo) returns no data or validation error
- No data available for far-future years beyond the calendar's coverage
- Service unavailability on Render free-tier cold starts may cause timeout

## How this service works

Returns index rebalancing and reconstitution dates (S&P 500, Nasdaq-100, Russell US semi-annual, DAX reviews) for a year: effective-after-close date and first trading day with new weights.

## Output

A list of rebalancing/reconstitution events for the requested index and year, each containing the index name, effective-after-close date, and the first trading day on which new weights apply.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "year": {
       "type": "string",
       "description": "Year, e.g. 2027"
      },
      "index": {
       "type": "string",
       "description": "SP500, NDX, RUSSELL, DAX or ALL"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/market-calendar-api-index-rebalancing-reconstitution-dates-ba7da847/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from market-calendar-api.onrender.com](https://www.zero.xyz/host/market-calendar-api.onrender.com/llms.txt)