# FastX402 Date Arithmetic

> FastX402 Date Arithmetic is a paid API for AI agents from fastx402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-17).

Adds or subtracts years, months, weeks, days, hours, minutes, and seconds to a date using calendar-correct rules, returning the ISO result and its weekday.

## Facts

- Endpoint: GET https://fastx402.tools/date-add?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-17
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastx402-date-arithmetic-60d86da7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_l894UE4wPQFJMrbPTl5pM

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 fastx402-date-arithmetic-60d86da7
```

Example prompt: What date is exactly 3 months after January 31, 2024, and what day of the week does it fall on? Use calendar-correct rules.

## When to prefer this

Choose this endpoint when you need calendar-correct date arithmetic — especially for month-end edge cases like January 31 + 1 month correctly yielding February 28 or 29 — and also want the resulting weekday returned alongside the ISO date, all in a single cheap call.

## Known failure modes

- Missing required 'date' query parameter returns an error
- Malformed date string (not ISO 8601) returns a parse error
- No duration parameters provided results in the same date returned
- Negative values larger than the date range may return invalid results

## How this service works

146 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.

## Output

A JSON object containing the original date in ISO 8601 format, the computed result date in ISO 8601 format, and the English name of the weekday of the result (e.g. Thursday).

## 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": [
      "date"
     ],
     "properties": {
      "date": {
       "type": "string",
       "description": "ISO 8601 date or date-time, e.g. 2024-01-31 or 2026-03-29T01:30:00Z"
      },
      "days": {
       "type": "string",
       "description": "days to add (negative to subtract)"
      },
      "hours": {
       "type": "string",
       "description": "hours to add (negative to subtract)"
      },
      "weeks": {
       "type": "string",
       "description": "weeks to add (negative to subtract)"
      },
      "years": {
       "type": "string",
       "description": "years to add (negative to subtract)"
      },
      "months": {
       "type": "string",
       "description": "months to add (negative to subtract)"
      },
      "minutes": {
       "type": "string",
       "description": "minutes to add (negative to subtract)"
      },
      "seconds": {
       "type": "string",
       "description": "seconds to add (negative to subtract)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "date": {
       "type": "string"
      },
      "result": {
       "type": "string"
      },
      "weekday": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "date": "2024-01-31T00:00:00.000Z",
  "result": "2024-02-29T00:00:00.000Z",
  "weekday": "Thursday"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastx402-date-arithmetic-60d86da7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fastx402.tools](https://www.zero.xyz/host/fastx402.tools/llms.txt)