Pregnancy Due Date Calculator 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

t4-242

Effect

Computation or source lookup only

Input and validation requirements

An extreme but valid-at-the-input-boundary JavaScript Date produces a due date beyond the representable Date range and must be rejected or reported as undefined. Additionally, an unlabelled slash-formatted date yields materially different results under MM/DD versus DD/MM conventions.

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": {
    "dating_method": "LMP",
    "last_menstrual_period": "2025-01-01",
    "as_of_date": "2025-02-12"
  },
  "expected_outputs": {
    "estimated_due_date": "2025-10-08",
    "gestational_age": "6w0d",
    "trimester": 1
  },
  "working": "Due date: 2025-01-01 + 280 days = 2025-10-08. Gestational age: 2025-02-12 - 2025-01-01 = 42 days. 42 / 7 = 6 weeks with 0 days remaining, so 6w0d. Since 6w0d is before 14w0d, trimester = 1."
}

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-tranche4/tranche4-results.json