fix: reject impossible calendar dates across catalog checks

site/checks.mjs

@@ -8,8 +8,8 @@
 
 import path from "node:path";
 import { parseStack, pickPath, StackError } from "./lib/stacks.mjs";
+import { isRealDate } from "./lib/shared.mjs";
 
-const DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
 const DATE_ANY_RE = /\d{4}-\d{2}-\d{2}/g;
 
 /** Generic hosts and distributors that are never a rights holder. */
@@ -144,7 +144,7 @@ export function checkAttributionConsistency(rel, meta, body, vocab) {
  * The check that defends the repo's central promise: a `verified` date may
  * never be newer than the evidence it claims to rest on. Bumping `verified`
  * without adding a dated Evidence line is exactly the failure this catches.
- * Also rejects Evidence dates in the future, and (V10) an Evidence section
+ * Also rejects impossible or future Evidence dates, and (V10) an Evidence section
  * that carries no date at all, whatever the entry's status.
  */
 export function checkEvidenceDates(rel, meta, body, today) {
@@ -156,12 +156,18 @@ export function checkEvidenceDates(rel, meta, body, today) {
     errors.push(`${rel} ## Evidence section carries no YYYY-MM-DD date`);
     return errors;
   }
-  const newest = dates[dates.length - 1];
+  const validDates = dates.filter((date) => {
+    if (isRealDate(date)) return true;
+    errors.push(`${rel} Evidence date ${date} is not a real YYYY-MM-DD date`);
+    return false;
+  });
+  if (!validDates.length) return errors;
+  const newest = validDates[validDates.length - 1];
   if (newest > today) {
     errors.push(`${rel} Evidence date ${newest} is in the future`);
   }
   const verified = empty(meta.verified) ? null : String(meta.verified);
-  if (verified && DATE_RE.test(verified) && verified > newest) {
+  if (isRealDate(verified) && verified > newest) {
     errors.push(
       `${rel} verified ${verified} is newer than its newest Evidence date ${newest}. ` +
         `A new verified date needs a dated Evidence line from the same check`

site/checks.test.mjs

@@ -157,6 +157,22 @@ accepts(
 );
 
 /* V8 / V10 -------------------------------------------------------------- */
+for (const date of ["2025-13-01", "2026-02-30", "2025-02-29", "1900-02-29", "2026-04-31"]) {
+  rejects(
+    `V8 rejects impossible Evidence date ${date}`,
+    checkEvidenceDates("bad.md", { verified: "2026-01-01" }, `# X${EV(date)}`, TODAY),
+    `Evidence date ${date} is not a real YYYY-MM-DD date`
+  );
+}
+rejects(
+  "V8 rejects an impossible date even alongside valid Evidence",
+  checkEvidenceDates("bad.md", { verified: "2026-09-20" }, `# X${EV("2026-02-30")}\n- Rechecked 2026-09-20.\n`, TODAY),
+  "Evidence date 2026-02-30 is not a real YYYY-MM-DD date"
+);
+accepts(
+  "V8 accepts real leap-day Evidence",
+  checkEvidenceDates("ok.md", { verified: "2000-02-29" }, `# X${EV("2000-02-29")}`, TODAY)
+);
 rejects(
   "V8 rejects a verified date newer than its newest Evidence date",
   checkEvidenceDates(

site/lib/lib.test.mjs

@@ -7,6 +7,7 @@ import {
   commercialLabel,
   entryPageUrl,
   esc,
+  isRealDate,
   STATUS_NOTES,
   verifiedAge,
 } from "./shared.mjs";
@@ -37,12 +38,21 @@ function throws(label, fn, needle) {
 }
 
 /* shared ----------------------------------------------------------------- */
+for (const date of ["2026-01-01", "2026-12-31", "2026-04-30", "2024-02-29", "2000-02-29", "0000-02-29", "0099-12-31"]) {
+  eq(`isRealDate accepts ${date}`, isRealDate(date), true);
+}
+for (const date of ["2025-13-01", "2026-02-30", "2025-02-29", "1900-02-29", "2100-02-29", "2026-04-31", "2026-00-01", "2026-01-00", "2026-01-32", "0099-02-29", "2026-1-01", "2026-01-1", "2026-01-01\n", " 2026-01-01", "2026-01-01T00:00:00Z", "", null, undefined, 20260101]) {
+  eq(`isRealDate rejects ${JSON.stringify(date)}`, isRealDate(date), false);
+}
 eq("esc escapes all five characters", esc(`<a href="x">'&'</a>`), "&lt;a href=&quot;x&quot;&gt;&#39;&amp;&#39;&lt;/a&gt;");
 eq("commercialLabel true", commercialLabel(true), "commercial OK");
 eq("commercialLabel varies", commercialLabel("varies"), "per-file review");
 eq("commercialLabel unknown", commercialLabel("unknown"), "commercial ?");
 eq("verifiedAge fresh", verifiedAge("2026-09-01", Date.parse("2026-09-24T00:00:00Z")).bucket, "fresh");
 eq("verifiedAge missing", verifiedAge(null, Date.now()).bucket, "unknown");
+for (const date of ["2025-13-01", "2026-02-30", "2025-02-29", "1900-02-29", "2026-04-31"]) {
+  eq(`verifiedAge rejects ${date}`, verifiedAge(date, Date.parse("2026-09-24T00:00:00Z")).bucket, "unknown");
+}
 eq("entryPageUrl trims the site slash", entryPageUrl({ siteUrl: "https://x.test/site/" }, "a-b"), "https://x.test/site/entry/a-b/");
 has("STATUS_NOTES covers needs-review", STATUS_NOTES["needs-review"], "open");
 
@@ -241,6 +251,10 @@ throws("licence in a why sentence", badStack((m) => m.replace("Five loops.", "Fi
 throws("licence phrase in a why sentence", badStack((m) => m.replace("Five loops.", "Five public domain loops.")), '("public domain")');
 throws("missing walked", badStack((m) => m.replace("walked: 2026-09-20\n", "")), "frontmatter is missing walked");
 throws("bad walked date", badStack((m) => m.replace("2026-09-20", "20 Sept")), "walked is not YYYY-MM-DD");
+for (const date of ["2025-13-01", "2026-02-30", "2025-02-29", "1900-02-29", "2026-04-31"]) {
+  throws(`impossible walked date ${date}`, badStack((m) => m.replace("2026-09-20", date)), "walked is not YYYY-MM-DD");
+}
+eq("leap-day walked date", parseStack(stackMd.replace("2026-09-20", "2000-02-29"), { file: "stacks/s1.md" }).meta.walked, "2000-02-29");
 throws("empty pick section", badStack((m) => m.replace("- **Music, no credit:** [Chips](../catalog/audio/subspaceaudio-5-chiptunes.md). Five loops.", "")), 'section "Audio" has no picks');
 throws("gaps line not a bullet", badStack((m) => m.replace("- No parallax layers yet.", "No parallax layers yet.")), "stacks/s1.md:24: a Gaps line is a bullet");
 eq("licence terms skip plain words", licenceTerms({ licenses: { custom: {}, MIT: { spdx: "MIT" }, CC0: { spdx: "CC0-1.0" } } }, ["OFL-1.1"]).sort().join(","), "CC0,CC0-1.0,MIT,OFL-1.1");

site/lib/shared.mjs

@@ -19,8 +19,18 @@ export const STATUS_NOTES = {
 const VERIFIED_FRESH_DAYS = 180;
 const VERIFIED_AGING_DAYS = 365;
 
+/** A real calendar date in strict YYYY-MM-DD form, independent of local time. */
+export function isRealDate(value) {
+  if (typeof value !== "string" || value.length !== 10 || !/^\d{4}-\d{2}-\d{2}$/.test(value)) return false;
+  const [year, month, day] = value.split("-").map(Number);
+  const date = new Date(0);
+  // Unlike Date.UTC, this preserves years 0000-0099.
+  date.setUTCFullYear(year, month - 1, day);
+  return date.getUTCFullYear() === year && date.getUTCMonth() === month - 1 && date.getUTCDate() === day;
+}
+
 export function verifiedAge(verified, now) {
-  if (!verified) return { days: null, bucket: "unknown" };
+  if (!isRealDate(verified)) return { days: null, bucket: "unknown" };
   const t = Date.parse(`${verified}T00:00:00Z`);
   if (Number.isNaN(t)) return { days: null, bucket: "unknown" };
   const days = Math.max(0, Math.floor((now - t) / 86400000));

site/lib/stacks.mjs

@@ -5,15 +5,14 @@
  */
 import fs from "node:fs";
 import path from "node:path";
-import { unquoteScalar } from "./shared.mjs";
+import { isRealDate, unquoteScalar } from "./shared.mjs";
 
 export class StackError extends Error {}
 
 /** The `##` sections a stack may have, in the order they must appear. */
 export const STACK_SECTIONS = ["Art", "Audio", "Fonts", "Tools", "Gaps"];
 
 const REQUIRED = ["id", "title", "task", "walked"];
-const DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
 // - **Need:** [Entry name](path/to/entry.md). Why this pick.
 const PICK_RE = /^- \*\*([^*]+?):\*\* \[([^\]]+)\]\(([^)\s]+)\)\.\s+(\S.*)$/;
 // Names and shorthands matched in any case, as whole words. The exact ids
@@ -99,7 +98,7 @@ export function parseStack(text, { file, terms = [] }) {
     metaLine[key] = i;
   }
   for (const key of REQUIRED) if (!meta[key]) fail(0, `frontmatter is missing ${key}`);
-  if (!DATE_RE.test(meta.walked)) fail(0, "walked is not YYYY-MM-DD");
+  if (!isRealDate(meta.walked)) fail(0, "walked is not YYYY-MM-DD (a real calendar date is required)");
   noLicence(metaLine.title, meta.title, "title");
   noLicence(metaLine.task, meta.task, "task");
 

site/validate.mjs

@@ -20,6 +20,7 @@ import {
   checkValueSpellings,
 } from "./checks.mjs";
 import { licenceTerms, listStackFiles } from "./lib/stacks.mjs";
+import { isRealDate } from "./lib/shared.mjs";
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 const ROOT = path.resolve(__dirname, "..");
@@ -81,7 +82,6 @@ const SKIP_WALK = new Set([".git", "node_modules", "dist", "RESEARCH"]);
 const ALLOWED_BINARY_PREFIXES = ["site/dist/", "docs/images/readme/"];
 const EMOJI_RE = /\p{Extended_Pictographic}/u;
 const MD_LINK_RE = /!\[[^\]]*\]\(([^)]+)\)|\[[^\]]*\]\(([^)]+)\)/g;
-const DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
 const EVIDENCE_DATE_RE = /\d{4}-\d{2}-\d{2}/;
 const COMMERCIAL_VALUES = new Set(["true", "false", "unknown", "varies"]);
 const STATUS_VALUES = new Set(["active", "needs-review", "deprecated"]);
@@ -315,7 +315,7 @@ function main() {
 
     if (meta.verified) {
       const v = String(meta.verified);
-      if (!DATE_RE.test(v)) errors.push(`${rel} verified is not YYYY-MM-DD`);
+      if (!isRealDate(v)) errors.push(`${rel} verified is not a real YYYY-MM-DD date`);
       else if (v > today) errors.push(`${rel} verified ${v} is in the future`);
     }