diff --git a/src/lib/order-age.test.ts b/src/lib/order-age.test.ts
new file mode 100644
index 0000000..9fb44df
--- /dev/null
+++ b/src/lib/order-age.test.ts
@@ -0,0 +1,114 @@
+import { describe, it, expect } from "vitest";
+import { getOrderAge, bucketToBadgeClass } from "./order-age";
+
+describe("getOrderAge", () => {
+  // Anchor `now` so the tests don't drift with wall-clock time.
+  // 2026-09-01 12:00 in Africa/Johannesburg = 2026-09-01T10:00:00Z
+  const NOW = new Date("2026-09-01T10:00:00.000Z");
+
+  it("returns daysOld=0 with label 'today' when created today", () => {
+    const result = getOrderAge("2026-09-01T08:00:00.000Z", NOW);
+    expect(result).toEqual({ daysOld: 0, bucket: "fresh", label: "today" });
+  });
+
+  it("returns daysOld=1 with bucket fresh for 1-day-old orders", () => {
+    const result = getOrderAge("2026-08-31T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(1);
+    expect(result.bucket).toBe("fresh");
+    expect(result.label).toBe("1d old");
+  });
+
+  it("returns daysOld=2 with bucket fresh at the upper edge of fresh", () => {
+    const result = getOrderAge("2026-08-30T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(2);
+    expect(result.bucket).toBe("fresh");
+    expect(result.label).toBe("2d old");
+  });
+
+  it("returns daysOld=3 with bucket recent at the lower edge of recent", () => {
+    const result = getOrderAge("2026-08-29T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(3);
+    expect(result.bucket).toBe("recent");
+    expect(result.label).toBe("3d old");
+  });
+
+  it("returns daysOld=7 with bucket recent at the upper edge of recent", () => {
+    const result = getOrderAge("2026-08-25T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(7);
+    expect(result.bucket).toBe("recent");
+    expect(result.label).toBe("7d old");
+  });
+
+  it("returns daysOld=8 with bucket slipping at the lower edge of slipping", () => {
+    const result = getOrderAge("2026-08-24T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(8);
+    expect(result.bucket).toBe("slipping");
+    expect(result.label).toBe("8d old");
+  });
+
+  it("returns daysOld=14 with bucket slipping at the upper edge of slipping", () => {
+    const result = getOrderAge("2026-08-18T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(14);
+    expect(result.bucket).toBe("slipping");
+    expect(result.label).toBe("14d old");
+  });
+
+  it("returns daysOld=15 with bucket stale at the lower edge of stale", () => {
+    const result = getOrderAge("2026-08-17T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(15);
+    expect(result.bucket).toBe("stale");
+    expect(result.label).toBe("15d old");
+  });
+
+  it("returns daysOld=365 with bucket stale for very old orders", () => {
+    const result = getOrderAge("2025-09-01T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(365);
+    expect(result.bucket).toBe("stale");
+    expect(result.label).toBe("365d old");
+  });
+
+  it("clamps future-dated created to daysOld=0 (clock skew tolerance)", () => {
+    const result = getOrderAge("2026-09-02T08:00:00.000Z", NOW);
+    expect(result.daysOld).toBe(0);
+    expect(result.bucket).toBe("fresh");
+    expect(result.label).toBe("today");
+  });
+
+  it("computes calendar-day delta in Africa/Johannesburg, not millisecond delta", () => {
+    // 23:00 SAST on 2026-08-31 (UTC+2) → 21:00 UTC
+    // 01:00 SAST on 2026-09-01 → 23:00 UTC on 2026-08-31
+    // Both are in the SAME calendar day in JNB (Sep 1 vs Aug 31).
+    // Millisecond delta is 2 hours, but the day delta must be 1.
+    const created = new Date("2026-08-31T21:00:00.000Z"); // 23:00 SAST Aug 31
+    const now = new Date("2026-08-31T23:00:00.000Z");     // 01:00 SAST Sep 1
+    const result = getOrderAge(created, now);
+    expect(result.daysOld).toBe(1);
+    expect(result.label).toBe("1d old");
+  });
+
+  it("treats an order created at 23:00 yesterday JNB and read at the same JNB day as today", () => {
+    // 23:00 SAST Aug 31 = 21:00 UTC Aug 31
+    // 21:00 SAST Aug 31 = 19:00 UTC Aug 31 — same JNB calendar day
+    const created = new Date("2026-08-31T21:00:00.000Z");
+    const sameDayNow = new Date("2026-08-31T19:00:00.000Z");
+    const result = getOrderAge(created, sameDayNow);
+    expect(result.daysOld).toBe(0);
+    expect(result.label).toBe("today");
+  });
+});
+
+describe("bucketToBadgeClass", () => {
+  it("returns a non-empty string for every bucket", () => {
+    expect(bucketToBadgeClass("fresh").length).toBeGreaterThan(0);
+    expect(bucketToBadgeClass("recent").length).toBeGreaterThan(0);
+    expect(bucketToBadgeClass("slipping").length).toBeGreaterThan(0);
+    expect(bucketToBadgeClass("stale").length).toBeGreaterThan(0);
+  });
+
+  it("is stable — same input returns same output", () => {
+    expect(bucketToBadgeClass("fresh")).toBe(bucketToBadgeClass("fresh"));
+    expect(bucketToBadgeClass("recent")).toBe(bucketToBadgeClass("recent"));
+    expect(bucketToBadgeClass("slipping")).toBe(bucketToBadgeClass("slipping"));
+    expect(bucketToBadgeClass("stale")).toBe(bucketToBadgeClass("stale"));
+  });
+});
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diff --git a/src/lib/order-age.ts b/src/lib/order-age.ts
new file mode 100644
index 0000000..9df4dfe
--- /dev/null
+++ b/src/lib/order-age.ts
@@ -0,0 +1,98 @@
+/**
+ * Order-age utility — calendar-day delta + colour-bucket mapping for
+ * the `/orders` list card age badge. See:
+ *   docs/superpowers/specs/2026-09-01-delivery-row-info-and-order-age-badge-design.md
+ *
+ * Why a separate util: keeps the page component free of date math;
+ * trivial to unit-test in isolation; pure function (no React, no PB).
+ */
+
+export type OrderAgeBucket = "fresh" | "recent" | "slipping" | "stale";
+
+export interface OrderAge {
+  /** Integer calendar-day delta. 0 means "today". Never negative. */
+  daysOld: number;
+  bucket: OrderAgeBucket;
+  /** Human-readable badge label. */
+  label: string;
+}
+
+/**
+ * Office timezone — the rest of the app doesn't deal in TZs explicitly,
+ * but the age badge reads "today" if the order was created on the same
+ * calendar day in JNB, not if it's been less than 24h since `created`.
+ * Hardcoded for now; centralise if a second locale ever needs it.
+ */
+const OFFICE_TZ = "Africa/Johannesburg";
+
+/**
+ * Format a Date as YYYY-MM-DD in the given IANA timezone.
+ * Used to compute the calendar-day delta independent of the
+ * machine's local timezone (vitest runs in UTC by default).
+ */
+function toLocalDayKey(d: Date, tz: string): string {
+  const parts = new Intl.DateTimeFormat("en-CA", {
+    timeZone: tz,
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+  }).formatToParts(d);
+  const y = parts.find((p) => p.type === "year")!.value;
+  const m = parts.find((p) => p.type === "month")!.value;
+  const day = parts.find((p) => p.type === "day")!.value;
+  return `${y}-${m}-${day}`;
+}
+
+/**
+ * Compute the age of an order relative to `now` (defaults to `new
+ * Date()`). The `daysOld` value is a **calendar-day** delta in the
+ * office's local timezone (Africa/Johannesburg) — an order created at
+ * 23:00 JNB yesterday read at 01:00 JNB today is `daysOld = 0`
+ * ("today"), not 1. The day delta is computed as
+ * `(localTodayKey - localCreatedKey)` parsed as UTC midnight dates
+ * and subtracted. Never returns a negative number; future-dated
+ * `created` values clamp to 0.
+ */
+export function getOrderAge(
+  created: string | Date,
+  now: Date = new Date(),
+): OrderAge {
+  const createdDate = typeof created === "string" ? new Date(created) : created;
+
+  const createdKey = toLocalDayKey(createdDate, OFFICE_TZ);
+  const todayKey = toLocalDayKey(now, OFFICE_TZ);
+
+  // Both keys parse as UTC midnight, so subtraction yields whole days.
+  const createdMs = new Date(`${createdKey}T00:00:00Z`).getTime();
+  const todayMs = new Date(`${todayKey}T00:00:00Z`).getTime();
+  const rawDays = Math.round((todayMs - createdMs) / 86_400_000);
+  const daysOld = rawDays < 0 ? 0 : rawDays;
+
+  let bucket: OrderAgeBucket;
+  if (daysOld <= 2) bucket = "fresh";
+  else if (daysOld <= 7) bucket = "recent";
+  else if (daysOld <= 14) bucket = "slipping";
+  else bucket = "stale";
+
+  const label = daysOld === 0 ? "today" : `${daysOld}d old`;
+
+  return { daysOld, bucket, label };
+}
+
+/**
+ * Map an age bucket to a tailwind className for the badge. Initial
+ * palette per the spec; centralise here so a future palette tweak is
+ * a one-line change.
+ */
+export function bucketToBadgeClass(bucket: OrderAgeBucket): string {
+  switch (bucket) {
+    case "fresh":
+      return "bg-emerald-100 text-emerald-800 dark:bg-emerald-950 dark:text-emerald-300";
+    case "recent":
+      return "bg-amber-100 text-amber-800 dark:bg-amber-950 dark:text-amber-300";
+    case "slipping":
+      return "bg-orange-100 text-orange-800 dark:bg-orange-950 dark:text-orange-300";
+    case "stale":
+      return "bg-red-100 text-red-800 dark:bg-red-950 dark:text-red-300";
+  }
+}
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