Cron Expression Explainer implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t6-022

Effect

Computation or source lookup only

Input and validation requirements

The specification leaves critical edge behavior undefined: an unsafe next-run count can cause precision loss or resource exhaustion, day-of-month/day-of-week matching has competing OR and AND interpretations, and repeated daylight-saving local times can yield different timestamps or run counts.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "expression": "*/15 9-17 * * 1-5",
    "dialect": "Vixie/POSIX 5-field",
    "timezone": "UTC",
    "start_timestamp": "2025-03-10T09:07:00Z",
    "next_count": 4
  },
  "expected_outputs": {
    "plain_english": "Every 15 minutes from 09:00 through 17:59, Monday through Friday.",
    "next_run_timestamps": [
      "2025-03-10T09:15:00Z",
      "2025-03-10T09:30:00Z",
      "2025-03-10T09:45:00Z",
      "2025-03-10T10:00:00Z"
    ]
  },
  "working": "2025-03-10 is Monday, so the weekday field matches. The hour range 9-17 includes 09:00 through 17:59. The minute step */15 produces minutes 0, 15, 30, 45. Starting strictly after 09:07, the first matching minute is 15: 09:15. Adding 15 minutes gives 09:30, then 09:45, then 10:00. Therefore the four outputs are 09:15, 09:30, 09:45, and 10:00 UTC."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json