web: drop leading empty month from the event calendar

web/src/lib/event.test.ts

@@ -78,6 +78,27 @@ describe("organizeEventsInCalendar", () => {
     expect(week["2026-07-12"]).toEqual([]);
   });
 
+  it("drops a leading month that only contains seeded padding days", () => {
+    // tirsdag 1. september 2026: the seeded week starts mandag 31. august
+    const events = getSingularEvents([
+      makeEvent("a", ["2026-09-04T17:00:00Z"]),
+      makeEvent("b", ["2026-10-02T17:00:00Z"]),
+    ]);
+
+    const calendar = organizeEventsInCalendar(events);
+
+    expect(Object.keys(calendar)).toEqual(["2026-09", "2026-10"]);
+    // the first week is still seeded with its September days
+    expect(Object.keys(calendar["2026-09"]["36"])).toEqual([
+      "2026-09-01",
+      "2026-09-02",
+      "2026-09-03",
+      "2026-09-04",
+      "2026-09-05",
+      "2026-09-06",
+    ]);
+  });
+
   it("splits a week across the year boundary under a shared week key", () => {
     const events = getSingularEvents([
       makeEvent("romjul", ["2026-12-30T20:00:00Z"]),

web/src/lib/event.ts

@@ -314,6 +314,19 @@ export function organizeEventsInCalendar<E extends EventListable>(
     calendar[yearMonth][week][day].push(event);
   });
 
+  // Seeding starts at the Monday of the first event's week, which can spill a
+  // few empty days into the previous month. Drop that leading empty month so
+  // the calendar starts at the first month that actually has events.
+  for (const yearMonth of Object.keys(calendar)) {
+    const hasEvents = Object.values(calendar[yearMonth]).some((week) =>
+      Object.values(week).some((day) => day.length > 0)
+    );
+    if (hasEvents) {
+      break;
+    }
+    delete calendar[yearMonth];
+  }
+
   return calendar;
 }