R008 — Hardcoded Dates

Purpose¶

R008 is designed to detect a date value hardcoded directly into the formula chain — the date-specific counterpart to R001 (Hardcoded Cells), which addresses numeric hardcodes. A typed date (a specific closing date, a period-end date) embedded in place of a reference to a controlled input cell carries the same structural risk as any other hardcoded assumption: it will not update if the model's actual date assumptions change elsewhere.

A Disclosed Current Limitation¶

As of engine version 2.1.0, R008 does not produce findings against real workbooks. This is stated here directly because it is stated directly in the rule's own source code, and AI_AUTHORITY_LAYER.md's governing standard for this documentation is to verify every technical claim against the implementation rather than describe intended behavior as though it were current behavior.

The specific gap: R008's detection logic checks for a hardcoded cell whose recorded value type is a date. The parsing stage that builds this value-type marker does not yet set it for date-valued cells — as of this writing, a cell holding a date value is recorded with a different value type at parse time. R008's own evaluation logic is implemented correctly against the engine's data model; the gap is in an earlier, upstream parsing step that has not yet been extended to recognize dates specifically.

Detection Logic (as designed)¶

Once the upstream parsing gap is closed, R008 will flag any cell recorded as both hardcoded (a typed constant, not a formula) and date-valued. No row-pattern comparison is involved, unlike R001 — R008 evaluates every date-typed hardcoded cell in the workbook directly, since a typed date in a formula chain is considered a risk regardless of what its neighboring cells contain.

Why It Matters¶

A hardcoded date embedded in a formula chain does not respond when the model's actual date assumptions — a deal closing date, a valuation date, a period-end date — change elsewhere in the model. This is the same underlying failure mode R001 addresses for numeric values, applied to dates: the model appears to update when its stated inputs change, while a formula depending on the hardcoded date silently continues to use the old value.

Evidence Produced¶

Once active, a triggered R008 finding's evidence would identify the specific sheet and cell address of the hardcoded date, its value, and a description stating that the cell contains a hardcoded date constant that should instead be referenced from a controlled input.

Severity¶

High (declared). Weight 7.5 (declared and already included in the SM-2.0 scoring basis, since the basis sums every active rule's declared weight regardless of whether the rule currently produces findings against real workbooks). R008 is not one of the five critical-override rules.

Example¶

Intended trigger, once the parsing gap is closed. A debt schedule formula reads =DAYS("2027-06-30",TODAY())/365 — the maturity date 2027-06-30 typed directly into the formula rather than referenced from a controlled input cell. Once R008's upstream value-type dependency is resolved, this cell would be flagged.

Current behavior. The same cell, evaluated against the engine today, is not flagged by R008, because the parsing stage does not yet mark it with the date value type R008's check depends on.

Recommended Remediation¶

Once active: replace the typed date with a reference to a named input cell holding the relevant date assumption (a maturity date, a valuation date, a closing date), consistent with the general remediation pattern for any hardcoded value.

Related Rules¶

R008 shares the Structural taxonomy category with the other Structural-category rules published in the Rule Reference, and shares its detection concept most directly with R001 — Hardcoded Cells — see the Rule Taxonomy page for the full category membership.

Related Articles¶

No existing Knowledge Centre technical guide addresses hardcoded date values specifically as of this writing; this section will be updated with a link in the same edit that publishes one.

Version History¶

No version-specific changes to R008's severity, weight, or category are recorded as of engine version 2.1.0. The parser limitation described above is a current, disclosed implementation gap, not a version history entry — this section will be updated once the gap is closed and R008 becomes active against real workbooks.