diff --git a/src/features/flights-map/calendarRange.test.ts b/src/features/flights-map/calendarRange.test.ts
new file mode 100644
index 00000000..6bba7806
--- /dev/null
+++ b/src/features/flights-map/calendarRange.test.ts
@@ -0,0 +1,114 @@
+import { describe, it, expect } from "vitest";
+import {
+  getMinDate,
+  getMaxDate,
+  buildDisabledDates,
+  findNextEnabledDate,
+} from "./calendarRange.js";
+
+function yyyymmdd(d: Date): string {
+  const y = d.getFullYear().toString();
+  const m = (d.getMonth() + 1).toString().padStart(2, "0");
+  const day = d.getDate().toString().padStart(2, "0");
+  return `${y}${m}${day}`;
+}
+
+function addDays(d: Date, n: number): Date {
+  const x = new Date(d);
+  x.setDate(x.getDate() + n);
+  x.setHours(0, 0, 0, 0);
+  return x;
+}
+
+describe("getMinDate / getMaxDate", () => {
+  it("minDate is today - 1 day, time zero'd", () => {
+    const today = new Date();
+    today.setHours(0, 0, 0, 0);
+    const expected = addDays(today, -1);
+    const min = getMinDate();
+    expect(min.getTime()).toBe(expected.getTime());
+    expect(min.getHours()).toBe(0);
+    expect(min.getMinutes()).toBe(0);
+    expect(min.getSeconds()).toBe(0);
+  });
+
+  it("maxDate is today + 6 months, time zero'd", () => {
+    const today = new Date();
+    today.setHours(0, 0, 0, 0);
+    const expected = new Date(today);
+    expected.setMonth(expected.getMonth() + 6);
+    const max = getMaxDate();
+    expect(max.getTime()).toBe(expected.getTime());
+  });
+});
+
+describe("buildDisabledDates", () => {
+  const min = new Date(2026, 0, 1);
+  const max = new Date(2026, 0, 5);
+
+  it("returns every day in the window when availableDays is empty", () => {
+    const disabled = buildDisabledDates(min, max, []);
+    expect(disabled.map((d) => d.getDate())).toEqual([1, 2, 3, 4, 5]);
+  });
+
+  it("returns [] when all dates in window are available", () => {
+    const available = ["20260101", "20260102", "20260103", "20260104", "20260105"];
+    expect(buildDisabledDates(min, max, available)).toEqual([]);
+  });
+
+  it("returns the exact complement for partial availability", () => {
+    const available = ["20260102", "20260104"];
+    const disabled = buildDisabledDates(min, max, available);
+    expect(disabled.map((d) => d.getDate())).toEqual([1, 3, 5]);
+  });
+
+  it("ignores availableDays entries outside the window", () => {
+    const available = ["20251231", "20260601", "20260103"];
+    const disabled = buildDisabledDates(min, max, available);
+    expect(disabled.map((d) => d.getDate())).toEqual([1, 2, 4, 5]);
+  });
+});
+
+describe("findNextEnabledDate", () => {
+  const min = new Date(2026, 0, 1);
+  const max = new Date(2026, 0, 5);
+
+  it("returns current when current is enabled", () => {
+    const current = new Date(2026, 0, 3);
+    const disabled = [new Date(2026, 0, 1), new Date(2026, 0, 2)];
+    const result = findNextEnabledDate(current, disabled, min, max);
+    expect(result?.getDate()).toBe(3);
+  });
+
+  it("advances to the next enabled date when current is disabled", () => {
+    const current = new Date(2026, 0, 2);
+    const disabled = [new Date(2026, 0, 1), new Date(2026, 0, 2), new Date(2026, 0, 3)];
+    const result = findNextEnabledDate(current, disabled, min, max);
+    expect(result?.getDate()).toBe(4);
+  });
+
+  it("returns null when every date in window is disabled", () => {
+    const current = new Date(2026, 0, 3);
+    const disabled = [
+      new Date(2026, 0, 1),
+      new Date(2026, 0, 2),
+      new Date(2026, 0, 3),
+      new Date(2026, 0, 4),
+      new Date(2026, 0, 5),
+    ];
+    expect(findNextEnabledDate(current, disabled, min, max)).toBeNull();
+  });
+
+  it("starts at minDate when current < minDate", () => {
+    const current = new Date(2025, 11, 25);
+    const disabled: Date[] = [];
+    const result = findNextEnabledDate(current, disabled, min, max);
+    expect(result?.getDate()).toBe(1);
+  });
+
+  it("returns null when current > maxDate", () => {
+    const current = new Date(2026, 1, 1);
+    const disabled: Date[] = [];
+    expect(findNextEnabledDate(current, disabled, min, max)).toBeNull();
+  });
+});
diff --git a/src/features/flights-map/calendarRange.ts b/src/features/flights-map/calendarRange.ts
new file mode 100644
index 00000000..7434259b
--- /dev/null
+++ b/src/features/flights-map/calendarRange.ts
@@ -0,0 +1,96 @@
+/**
+ * Calendar helpers for the flights-map filter date picker.
+ *
+ * All dates are treated as date-only (time zero'd) for day-level comparisons.
+ * minDate/maxDate form the selectable window; `buildDisabledDates` produces
+ * the complement of `availableDays` over that window; `findNextEnabledDate`
+ * advances a current selection forward until it lands on an enabled day.
+ *
+ * Matches Angular `FlightsMapFiltersStateService` calendar behavior.
+ */
+
+/** Today with time set to 00:00:00 local. */
+export function today(): Date {
+  const d = new Date();
+  d.setHours(0, 0, 0, 0);
+  return d;
+}
+
+/** minDate = today - 1 day (Angular parity). */
+export function getMinDate(): Date {
+  const d = today();
+  d.setDate(d.getDate() - 1);
+  return d;
+}
+
+/** maxDate = today + 6 months (Angular parity). */
+export function getMaxDate(): Date {
+  const d = today();
+  d.setMonth(d.getMonth() + 6);
+  return d;
+}
+
+/**
+ * Every date in [minDate, maxDate] whose yyyymmdd is NOT in `availableDays`.
+ * When `availableDays` is empty, every date in the range is disabled.
+ */
+export function buildDisabledDates(
+  minDate: Date,
+  maxDate: Date,
+  availableDays: ReadonlyArray<string>,
+): Date[] {
+  const available = new Set(availableDays);
+  const disabled: Date[] = [];
+  const cursor = new Date(minDate);
+  cursor.setHours(0, 0, 0, 0);
+  const end = new Date(maxDate);
+  end.setHours(0, 0, 0, 0);
+  while (cursor.getTime() <= end.getTime()) {
+    const key = toYyyymmdd(cursor);
+    if (!available.has(key)) disabled.push(new Date(cursor));
+    cursor.setDate(cursor.getDate() + 1);
+  }
+  return disabled;
+}
+
+/**
+ * Advances `current` day-by-day until it hits a non-disabled date, staying
+ * within [minDate, maxDate]. Returns `null` if no enabled date exists.
+ * `current` itself is tested first. If `current < minDate`, starts at minDate.
+ */
+export function findNextEnabledDate(
+  current: Date,
+  disabledDates: ReadonlyArray<Date>,
+  minDate: Date,
+  maxDate: Date,
+): Date | null {
+  const disabledSet = new Set(
+    disabledDates.map((d) => {
+      const x = new Date(d);
+      x.setHours(0, 0, 0, 0);
+      return x.getTime();
+    }),
+  );
+  const min = new Date(minDate);
+  min.setHours(0, 0, 0, 0);
+  const max = new Date(maxDate);
+  max.setHours(0, 0, 0, 0);
+
+  const cursor = new Date(current);
+  cursor.setHours(0, 0, 0, 0);
+
+  if (cursor.getTime() < min.getTime()) cursor.setTime(min.getTime());
+
+  while (cursor.getTime() <= max.getTime()) {
+    if (!disabledSet.has(cursor.getTime())) return new Date(cursor);
+    cursor.setDate(cursor.getDate() + 1);
+  }
+  return null;
+}
+
+function toYyyymmdd(d: Date): string {
+  const y = d.getFullYear().toString();
+  const m = (d.getMonth() + 1).toString().padStart(2, "0");
+  const day = d.getDate().toString().padStart(2, "0");
+  return `${y}${m}${day}`;
+}