diff --git a/web/src/legal.test.ts b/web/src/legal.test.ts
index f37752a..8f56717 100644
--- a/web/src/legal.test.ts
+++ b/web/src/legal.test.ts
@@ -30,12 +30,18 @@ describe("dayOfYear", () => {
     expect(dayOfYear(new Date(2026, 11, 31))).toBe(365);
   });
 
-  // Characterizes CURRENT (mismatched) behavior: dayOfYear uses the real
-  // calendar (366 in a leap year) while the pipeline's _doy uses a fixed
-  // non-leap table (max 365). Plan 004 reconciles these; when it does,
-  // this assertion must change to reflect the new convention.
-  it("returns 366 for Dec 31 in a leap year (current mismatched behavior)", () => {
-    expect(dayOfYear(new Date(2028, 11, 31))).toBe(366);
+  // non-leap convention — must match pipeline/normalize.py _MONTH_START
+  it("returns 365 for Dec 31 in a leap year (non-leap convention)", () => {
+    expect(dayOfYear(new Date(2028, 11, 31))).toBe(365);
+  });
+
+  it("Feb 29 maps to the same value as Mar 1 (non-leap convention)", () => {
+    expect(dayOfYear(new Date(2028, 1, 29))).toBe(60);
+    expect(dayOfYear(new Date(2028, 2, 1))).toBe(60);
+  });
+
+  it("matches the pipeline's parse_window start for 05/01 (cross-convention anchor)", () => {
+    expect(dayOfYear(new Date(2026, 4, 1))).toBe(121);
   });
 });
 
@@ -135,4 +141,9 @@ describe("isOpen (combined)", () => {
   it("permitted class and in season -> true", () => {
     expect(evalOpen(["passenger"], 200, props)).toBe(true);
   });
+
+  it("a window ending 12/31 (open_end=365) is OPEN on Dec 31 of a leap year (the leap-year bug this plan fixes)", () => {
+    const leapProps = { classes: ",passenger,", season: "seasonal", open_start: 121, open_end: 365 };
+    expect(evalOpen(["passenger"], dayOfYear(new Date(2028, 11, 31)), leapProps)).toBe(true);
+  });
 });
diff --git a/web/src/legal.ts b/web/src/legal.ts
index d92c0a4..35788d1 100644
--- a/web/src/legal.ts
+++ b/web/src/legal.ts
@@ -4,16 +4,20 @@
 // Mirrors the data model from pipeline/normalize.py:
 //   classes     ",passenger,motorcycle,"   (comma-delimited token list)
 //   season      "yearlong" | "seasonal"
-//   open_start  day-of-year 1..366
-//   open_end    day-of-year 1..366  (may be < open_start for winter-wrapping)
+//   open_start  day-of-year 1..365 (non-leap convention)
+//   open_end    day-of-year 1..365 (non-leap convention)  (may be < open_start for winter-wrapping)
 
 import type { ExpressionSpecification } from "maplibre-gl";
 
-/** Day-of-year (1..366) for a JS Date, in local time. */
+// Cumulative day-of-year for the 1st of each month (non-leap); index 1..12.
+// MUST match _MONTH_START in pipeline/normalize.py — the tiles encode season
+// windows with this table, so the frontend has to count days the same way.
+// Feb 29 intentionally maps to 60 (== Mar 1), same as the pipeline.
+const MONTH_START = [0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
+
+/** Day-of-year (1..365, non-leap convention) for a JS Date, in local time. */
 export function dayOfYear(d: Date): number {
-  const start = new Date(d.getFullYear(), 0, 0);
-  const diff = d.getTime() - start.getTime();
-  return Math.floor(diff / 86_400_000);
+  return MONTH_START[d.getMonth() + 1] + d.getDate();
 }
 
 /** True-expression: the route permits ANY of the profile's class tokens.
diff --git a/web/src/main.ts b/web/src/main.ts
index 1c01779..b2e5765 100644
--- a/web/src/main.ts
+++ b/web/src/main.ts
@@ -111,7 +111,11 @@ for (const p of VEHICLE_PROFILES) {
 const paramVehicle = new URLSearchParams(location.search).get("vehicle");
 vehicleSel.value =
   VEHICLE_PROFILES.some((p) => p.key === paramVehicle) ? paramVehicle! : "moto_plated";
-dateInput.value = new Date().toISOString().slice(0, 10);
+// Local date, not the UTC ISO date string: in the evening (UTC is past
+// midnight) the default must still be *today* here — "the night before" is
+// the primary use.
+const now = new Date();
+dateInput.value = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}-${String(now.getDate()).padStart(2, "0")}`;
 hideClosed.checked = new URLSearchParams(location.search).get("hideclosed") === "1";
 
 function selectedTokens(): string[] {