# WebberSites Date Arithmetic API

> WebberSites Date Arithmetic API is a paid API for AI agents from api.webbersites.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Performs exact calendar math: differences between dates (days/business days/weeks/hours), date addition/subtraction with business-day support, and date metadata lookup (weekday, ISO week, day-of-year, leap year, unix timestamp).

## Facts

- Endpoint: GET https://api.webbersites.com/api/calc/dates
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/webbersites-date-arithmetic-api-1f16f7c7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wNMJuLJLLT_8kU25E-ghZ

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 webbersites-date-arithmetic-api-1f16f7c7
```

Example prompt: How many business days are there between March 15 and April 30, 2025, and what date lands exactly 10 business days after April 30?

## When to prefer this

Use this endpoint whenever precise calendar math is required — especially when business-day counting, month/year offsets, or real-calendar validation (rejecting Feb 30) matter. Prefer this over asking an LLM to compute dates directly, since LLMs are prone to off-by-one errors and business-day miscounts. Ideal for scheduling, deadline calculation, SLA tracking, or any workflow requiring deterministic date results.

## Known failure modes

- Invalid date string (e.g. Feb 30) — rejected with a validation error
- Missing required query parameters for the chosen operation mode
- Malformed duration expression in 'add' parameter (e.g. unsupported unit)
- Network or upstream server error returning a non-200 response

## How this service works

Exact date arithmetic — the calendar math LLMs guess at. ?from=&to= → days, business days, weeks, hours between; ?date=&add=30d|2w|3m|1y|10bd → the resulting date (bd = business days); ?date= alone → weekday, ISO week, day-of-year, leap year, unix. All UTC, Mon-Fri business days, real-calendar validation (Feb 30 is rejected).

## Output

A JSON object containing one or more of: diff (days, business days, weeks, hours between two dates), result (the date after adding/subtracting a duration), or date metadata (weekday, ISO week number, day-of-year, leap year boolean, unix timestamp). Invalid inputs like Feb 30 are rejected with a validation error.

## 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",
     "properties": {
      "to": {
       "type": "string"
      },
      "add": {
       "type": "string",
       "description": "e.g. 30d, -2w, 3m, 1y, 10bd"
      },
      "date": {
       "type": "string",
       "description": "ISO date — alone: info; with add: arithmetic"
      },
      "from": {
       "type": "string",
       "description": "ISO date — with to: difference"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "to": {
       "type": "object"
      },
      "date": {
       "type": "object"
      },
      "diff": {
       "type": "object"
      },
      "from": {
       "type": "object"
      },
      "result": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "to": {
   "date": "2026-12-25",
   "weekday": "Friday"
  },
  "diff": {
   "days": 169,
   "weeks": 24.14,
   "business_days": 121
  },
  "from": {
   "date": "2026-07-09",
   "weekday": "Thursday"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/webbersites-date-arithmetic-api-1f16f7c7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.webbersites.com](https://www.zero.xyz/host/api.webbersites.com/llms.txt)