fix(util): parseDate rejects calendar-invalid dates (Feb 30, Feb 29 non-leap, Apr 31, ...)

src/util/parseDate.test.ts

@@ -44,6 +44,52 @@ describe("parseDate", () => {
     expect(parseDate("20250101")).toEqual({ year: 2025, month: "01", day: "01" });
     expect(parseDate("20251231")).toEqual({ year: 2025, month: "12", day: "31" });
   });
+
+  it("rejects Feb 30 in any year", () => {
+    // Without the calendar probe, `new Date("2025-02-30")` silently rolls to
+    // March 2 — corrupting ChangeLog / spac_history point-in-time semantics.
+    expect(() => parseDate("2025-02-30")).toThrow(/Invalid calendar date/);
+    expect(() => parseDate("2024-02-30")).toThrow(/Invalid calendar date/);
+  });
+
+  it("rejects Feb 29 in a non-leap year but accepts it in a leap year", () => {
+    expect(() => parseDate("2025-02-29")).toThrow(/Invalid calendar date/);
+    expect(() => parseDate("2023-02-29")).toThrow(/Invalid calendar date/);
+    // 1900 is not a leap year (divisible by 100, not by 400).
+    expect(() => parseDate("1900-02-29")).toThrow(/Invalid calendar date/);
+    // 2024 is a leap year; 2000 is a leap year (divisible by 400).
+    expect(parseDate("2024-02-29")).toEqual({ year: 2024, month: "02", day: "29" });
+    expect(parseDate("2000-02-29")).toEqual({ year: 2000, month: "02", day: "29" });
+  });
+
+  it.each([
+    ["2025-04-31", 4],
+    ["2025-06-31", 6],
+    ["2025-09-31", 9],
+    ["2025-11-31", 11],
+  ])("rejects the impossible 31st of a 30-day month (%s)", (input) => {
+    expect(() => parseDate(input)).toThrow(/Invalid calendar date/);
+  });
+
+  it.each([
+    ["2025-00-10"], // month 0
+    ["2025-13-10"], // month 13
+    ["2025-01-00"], // day 0
+    ["2025-01-32"], // day 32
+  ])("rejects out-of-range month/day (%s)", (input) => {
+    expect(() => parseDate(input)).toThrow("Invalid date format");
+  });
+
+  it("accepts all four supported formats for a valid date", () => {
+    // Regression fence: the calendar probe must not reject any of the
+    // recognised shapes for a well-formed real date.
+    const expected = { year: 2024, month: "02", day: "29" };
+    expect(parseDate("2024-02-29")).toEqual(expected);
+    expect(parseDate("2024/02/29")).toEqual(expected);
+    expect(parseDate("02/29/2024")).toEqual(expected);
+    expect(parseDate("02-29-2024")).toEqual(expected);
+    expect(parseDate("20240229")).toEqual(expected);
+  });
 });
 
 describe("secDate", () => {

src/util/parseDate.ts

@@ -47,6 +47,21 @@ export function parseDate(dateStr: string): { year: number; month: string; day:
         throw new Error("Invalid date format");
       }
 
+      // Range-valid but calendar-invalid dates (Feb 30, Feb 29 in non-leap
+      // years, Apr/Jun/Sep/Nov 31) would otherwise flow through as-is and
+      // silently roll forward when downstream code hands the string to
+      // `new Date(...)` — shifting point-in-time semantics of ChangeLog /
+      // spac_history / offering-history rows. Probe via a UTC Date and reject
+      // any input the calendar refused to preserve.
+      const probe = new Date(Date.UTC(year, month - 1, day));
+      if (
+        probe.getUTCFullYear() !== year ||
+        probe.getUTCMonth() !== month - 1 ||
+        probe.getUTCDate() !== day
+      ) {
+        throw new Error(`Invalid calendar date: ${dateStr}`);
+      }
+
       return {
         year,
         month: month.toString().padStart(2, "0"),