# Calendar Systems – Leap Year Checker

> Calendar Systems – Leap Year Checker is a paid API for AI agents from calendar-systems.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Determines whether a given year is a leap year in the Gregorian, Julian, Hebrew, Islamic (tabular), or Persian calendar, and returns the applicable rule plus adjacent leap years.

## Facts

- Endpoint: GET https://calendar-systems.x402tookit.com/leap-year?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/calendar-systems-leap-year-checker-49c327a1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XHid0JUs3M5QuhSqGBajZ

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-leap-year-checker-49c327a1
```

Example prompt: Is 1900 a leap year in the Julian calendar? Also tell me which leap years are nearby and what rule applies.

## When to prefer this

Use this endpoint when you need calendar-system-specific leap year logic beyond just the Gregorian calendar — particularly for historical dates under the Julian calendar, Jewish/Hebrew calendar computations, Islamic tabular calendar scheduling, or Persian Solar Hijri date arithmetic. It also provides adjacent leap years and rule explanations, making it ideal for educational or historical research contexts rather than a simple yes/no check.

## Known failure modes

- Missing required 'year' parameter returns an error
- Invalid calendar enum value (not one of gregorian/julian/hebrew/islamic/persian) returns a validation error
- Extremely large or small year values may return degraded results or null fields
- Non-integer year values will fail schema validation

## How this service works

Is a year a leap year in the Gregorian, Julian, Hebrew, Islamic (tabular) or Persian calendar? Rule and nearby leap years.

## Output

Returns a boolean leapYear verdict, the calendar-specific rule as a string, a plain-language summary, the number of days in the year, the previous and next leap years, the leap cycle name, and optional disclaimer or degraded-mode 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": "Year number in the chosen calendar"
      },
      "calendar": {
       "enum": [
        "gregorian",
        "julian",
        "hebrew",
        "islamic",
        "persian"
       ],
       "type": "string",
       "description": "gregorian (default), julian, hebrew, islamic or persian"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "rule": {
       "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"
       ]
      },
      "calendar": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "leapYear": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "leapCycle": {
       "type": [
        "null",
        "string"
       ]
      },
      "daysInYear": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "nextLeapYear": {
       "type": [
        "null",
        "number"
       
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/calendar-systems-leap-year-checker-49c327a1/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)