diff --git a/ApiCore-Frontend/src/app/(app)/calendar/page.tsx b/ApiCore-Frontend/src/app/(app)/calendar/page.tsx
index 7e1df7d..00db797 100644
--- a/ApiCore-Frontend/src/app/(app)/calendar/page.tsx
+++ b/ApiCore-Frontend/src/app/(app)/calendar/page.tsx
@@ -20,6 +20,8 @@ import { CalendarEvent, CalendarEventType } from "@/lib/calendar/types";
 import { fetchApiaries } from "@/lib/apiaries/api";
 import { Button } from "@/components/ui/button";
 import { PageHeader } from "@/components/page-header";
+import { EmptyState } from "@/components/empty-state";
+import { ErrorState, LoadingState } from "@/components/query-state";
 import {
   Select,
   SelectContent,
@@ -27,25 +29,17 @@ import {
   SelectTrigger,
   SelectValue,
 } from "@/components/ui/select";
+import { cn } from "@/lib/utils";
 
 const WEEKDAYS = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"];
 
-const EVENT_ICON: Record<CalendarEventType, LucideIcon> = {
-  TASK: ListTodo,
-  INSPECTION: ClipboardCheck,
-  TREATMENT: Syringe,
-  FEEDING: Droplet,
-  HARVEST: Package,
-  QUEEN_ASSIGNMENT: Crown,
-};
-
-const EVENT_TONE: Record<CalendarEventType, string> = {
-  TASK: "bg-secondary/15 text-secondary",
-  INSPECTION: "bg-primary/15 text-primary",
-  TREATMENT: "bg-destructive/15 text-destructive",
-  FEEDING: "bg-warning/20 text-warning-foreground",
-  HARVEST: "bg-primary/15 text-primary",
-  QUEEN_ASSIGNMENT: "bg-secondary/15 text-secondary",
+const EVENT_META: Record<CalendarEventType, { icon: LucideIcon; label: string; tone: string }> = {
+  TASK: { icon: ListTodo, label: "Aufgabe", tone: "bg-secondary/15" },
+  INSPECTION: { icon: ClipboardCheck, label: "Durchsicht", tone: "bg-primary/15" },
+  TREATMENT: { icon: Syringe, label: "Behandlung", tone: "bg-destructive/15" },
+  FEEDING: { icon: Droplet, label: "Fütterung", tone: "bg-warning/20" },
+  HARVEST: { icon: Package, label: "Ernte", tone: "bg-primary/15" },
+  QUEEN_ASSIGNMENT: { icon: Crown, label: "Königin", tone: "bg-secondary/15" },
 };
 
 function eventHref(event: CalendarEvent): string | null {
@@ -56,8 +50,11 @@ function eventHref(event: CalendarEvent): string | null {
   return null;
 }
 
+/** Local calendar day "2026-10-01" (not UTC - late evening entries stay on their day). */
 function toDateKey(date: Date): string {
-  return date.toISOString().slice(0, 10);
+  const month = String(date.getMonth() + 1).padStart(2, "0");
+  const day = String(date.getDate()).padStart(2, "0");
+  return `${date.getFullYear()}-${month}-${day}`;
 }
 
 function startOfMonth(date: Date): Date {
@@ -71,9 +68,69 @@ function startOfGrid(monthStart: Date): Date {
   return gridStart;
 }
 
+function dayHeading(date: Date): string {
+  return date.toLocaleDateString("de-DE", { weekday: "long", day: "numeric", month: "long" });
+}
+
+function EventRow({ event }: { event: CalendarEvent }) {
+  const meta = EVENT_META[event.type];
+  const Icon = meta.icon;
+  const href = eventHref(event);
+  const content = (
+    <span className={cn("flex min-h-11 items-center gap-2 rounded-lg px-3 text-sm", meta.tone)}>
+      <Icon className="size-4 shrink-0" aria-hidden />
+      <span className="shrink-0 text-xs font-medium text-muted-foreground">{meta.label}</span>
+      <span className="truncate">{event.title}</span>
+    </span>
+  );
+  return href ? (
+    <Link href={href} className="block rounded-lg focus-visible:ring-3 focus-visible:ring-ring/50">
+      {content}
+    </Link>
+  ) : (
+    content
+  );
+}
+
+function DayEvents({
+  date,
+  events,
+  isToday,
+}: {
+  date: Date;
+  events: CalendarEvent[];
+  isToday: boolean;
+}) {
+  return (
+    <section className="flex flex-col gap-2">
+      <h2 className="flex items-center gap-2 text-sm font-semibold">
+        {dayHeading(date)}
+        {isToday ? (
+          <span className="rounded-full bg-primary px-2 py-0.5 text-xs text-primary-foreground">
+            Heute
+          </span>
+        ) : null}
+      </h2>
+      {events.length === 0 ? (
+        <p className="text-sm text-muted-foreground">Nichts eingetragen.</p>
+      ) : (
+        <ul className="flex flex-col gap-1.5">
+          {events.map((event) => (
+            <li key={event.id}>
+              <EventRow event={event} />
+            </li>
+          ))}
+        </ul>
+      )}
+    </section>
+  );
+}
+
 export default function CalendarPage() {
   const [month, setMonth] = useState(() => startOfMonth(new Date()));
   const [apiaryId, setApiaryId] = useState("");
+  const [selectedKey, setSelectedKey] = useState(() => toDateKey(new Date()));
+  const todayKey = toDateKey(new Date());
 
   const monthStart = startOfMonth(month);
   const gridStart = startOfGrid(monthStart);
@@ -87,7 +144,7 @@ export default function CalendarPage() {
     queryKey: ["apiaries"],
     queryFn: () => fetchApiaries(),
   });
-  const { data: events, isLoading, isError } = useQuery({
+  const eventsQuery = useQuery({
     queryKey: ["calendar", monthStart.toISOString(), apiaryId],
     queryFn: () =>
       fetchCalendarEvents({
@@ -99,129 +156,197 @@ export default function CalendarPage() {
 
   const eventsByDay = useMemo(() => {
     const map = new Map<string, CalendarEvent[]>();
-    for (const event of events ?? []) {
-      const key = event.date.slice(0, 10);
+    for (const event of eventsQuery.data ?? []) {
+      const key = toDateKey(new Date(event.date));
       const bucket = map.get(key) ?? [];
       bucket.push(event);
       map.set(key, bucket);
     }
     return map;
-  }, [events]);
+  }, [eventsQuery.data]);
+
+  const daysOfMonthWithEvents = gridDays.filter(
+    (day) =>
+      day.getMonth() === month.getMonth() && (eventsByDay.get(toDateKey(day))?.length ?? 0) > 0,
+  );
+  const selectedDay = gridDays.find((day) => toDateKey(day) === selectedKey);
+
+  function goToMonth(offset: number) {
+    setMonth(new Date(month.getFullYear(), month.getMonth() + offset, 1));
+  }
+
+  function goToToday() {
+    setMonth(startOfMonth(new Date()));
+    setSelectedKey(todayKey);
+  }
+
+  const monthLabel = month.toLocaleDateString("de-DE", { month: "long", year: "numeric" });
 
   return (
     <main className="flex flex-col gap-4 p-4 sm:p-6">
       <PageHeader
         icon={CalendarDays}
-        title={month.toLocaleDateString("de-DE", { month: "long", year: "numeric" })}
-        description="Kalender"
+        title="Kalender"
+        description="Was wann ansteht und was erledigt wurde – Monat für Monat."
         gradient="var(--gradient-sky)"
-        actions={
-          <div className="flex items-center gap-2">
-          <Select
-            value={apiaryId || "ALL"}
-            onValueChange={(value) => setApiaryId(value === "ALL" ? "" : (value ?? ""))}
-          >
-            <SelectTrigger className="w-44">
-              <SelectValue placeholder="Alle Bienenstände">
-                {apiaryId
-                  ? (apiaries?.find((apiary) => apiary.id === apiaryId)?.name ?? apiaryId)
-                  : "Alle Bienenstände"}
-              </SelectValue>
-            </SelectTrigger>
-            <SelectContent>
-              <SelectItem value="ALL">Alle Bienenstände</SelectItem>
-              {apiaries?.map((apiary) => (
-                <SelectItem key={apiary.id} value={apiary.id}>
-                  {apiary.name}
-                </SelectItem>
-              ))}
-            </SelectContent>
-          </Select>
-          <Button
-            variant="outline"
-            size="icon"
-            aria-label="Vorheriger Monat"
-            onClick={() => setMonth(new Date(month.getFullYear(), month.getMonth() - 1, 1))}
-          >
-            <ChevronLeft className="size-4" />
-          </Button>
-          <Button
-            variant="outline"
-            size="icon"
-            aria-label="Nächster Monat"
-            onClick={() => setMonth(new Date(month.getFullYear(), month.getMonth() + 1, 1))}
-          >
-            <ChevronRight className="size-4" />
-          </Button>
-          </div>
-        }
       />
 
-      {isLoading ? <p className="text-sm text-muted-foreground">Lädt…</p> : null}
-      {isError ? (
-        <p role="alert" className="text-sm text-destructive">
-          Kalender konnte nicht geladen werden.
+      <div className="flex flex-wrap items-center gap-2">
+        <Button
+          variant="outline"
+          size="touch"
+          aria-label="Vorheriger Monat"
+          onClick={() => goToMonth(-1)}
+        >
+          <ChevronLeft aria-hidden />
+        </Button>
+        <p className="min-w-40 text-center font-heading text-lg font-semibold" aria-live="polite">
+          {monthLabel}
         </p>
+        <Button
+          variant="outline"
+          size="touch"
+          aria-label="Nächster Monat"
+          onClick={() => goToMonth(1)}
+        >
+          <ChevronRight aria-hidden />
+        </Button>
+        <Button variant="ghost" size="touch" onClick={goToToday}>
+          Heute
+        </Button>
+        <Select
+          value={apiaryId || "ALL"}
+          onValueChange={(value) => setApiaryId(value === "ALL" ? "" : (value ?? ""))}
+        >
+          <SelectTrigger className="w-full sm:ml-auto sm:w-52" aria-label="Bienenstand">
+            <SelectValue placeholder="Alle Bienenstände">
+              {apiaryId
+                ? (apiaries?.find((apiary) => apiary.id === apiaryId)?.name ?? apiaryId)
+                : "Alle Bienenstände"}
+            </SelectValue>
+          </SelectTrigger>
+          <SelectContent>
+            <SelectItem value="ALL">Alle Bienenstände</SelectItem>
+            {apiaries?.map((apiary) => (
+              <SelectItem key={apiary.id} value={apiary.id}>
+                {apiary.name}
+              </SelectItem>
+            ))}
+          </SelectContent>
+        </Select>
+      </div>
+
+      {eventsQuery.isLoading ? <LoadingState what="Einträge" /> : null}
+      {eventsQuery.isError ? (
+        <ErrorState
+          what="Kalendereinträge"
+          onRetry={() => void eventsQuery.refetch()}
+          isRetrying={eventsQuery.isFetching}
+        />
       ) : null}
 
-      <div className="grid grid-cols-7 overflow-hidden rounded-xl border">
-        {WEEKDAYS.map((weekday) => (
-          <div
-            key={weekday}
-            className="border-b bg-muted px-2 py-1.5 text-center text-xs font-medium text-muted-foreground"
-          >
-            {weekday}
+      {eventsQuery.data ? (
+        <>
+          {/* Phones: a plain list of the days that have something on. */}
+          <div className="flex flex-col gap-5 sm:hidden">
+            {daysOfMonthWithEvents.length === 0 ? (
+              <EmptyState icon={CalendarDays} title={`Im ${monthLabel} steht nichts an.`} />
+            ) : (
+              daysOfMonthWithEvents.map((day) => (
+                <DayEvents
+                  key={toDateKey(day)}
+                  date={day}
+                  events={eventsByDay.get(toDateKey(day)) ?? []}
+                  isToday={toDateKey(day) === todayKey}
+                />
+              ))
+            )}
           </div>
-        ))}
-        {gridDays.map((day) => {
-          const key = toDateKey(day);
-          const dayEvents = eventsByDay.get(key) ?? [];
-          const isCurrentMonth = day.getMonth() === month.getMonth();
-          const isToday = key === toDateKey(new Date());
-          return (
-            <div
-              key={key}
-              className={`flex min-h-24 flex-col gap-1 border-r border-b p-1.5 last:border-r-0 ${
-                isCurrentMonth ? "bg-card" : "bg-muted/40"
-              }`}
-            >
-              <span
-                className={`text-xs ${isCurrentMonth ? "text-foreground" : "text-muted-foreground"} ${
-                  isToday ? "font-semibold text-primary" : ""
-                }`}
-              >
-                {day.getDate()}
-              </span>
-              <div className="flex flex-col gap-1">
-                {dayEvents.slice(0, 3).map((event) => {
-                  const Icon = EVENT_ICON[event.type];
-                  const href = eventHref(event);
-                  const content = (
+
+          {/* Wider screens: month grid; choosing a day lists all its entries below. */}
+          <div className="hidden flex-col gap-4 sm:flex">
+            <div className="grid grid-cols-7 overflow-hidden rounded-xl border">
+              {WEEKDAYS.map((weekday) => (
+                <div
+                  key={weekday}
+                  className="border-b bg-muted px-2 py-1.5 text-center text-xs font-medium text-muted-foreground"
+                >
+                  {weekday}
+                </div>
+              ))}
+              {gridDays.map((day) => {
+                const key = toDateKey(day);
+                const dayEvents = eventsByDay.get(key) ?? [];
+                const isCurrentMonth = day.getMonth() === month.getMonth();
+                const isToday = key === todayKey;
+                const isSelected = key === selectedKey;
+                return (
+                  <button
+                    key={key}
+                    type="button"
+                    onClick={() => setSelectedKey(key)}
+                    aria-pressed={isSelected}
+                    aria-label={`${dayHeading(day)}${isToday ? ", heute" : ""}: ${dayEvents.length} Einträge`}
+                    className={cn(
+                      "flex min-h-24 flex-col gap-1 border-r border-b p-1.5 text-left last:border-r-0",
+                      isCurrentMonth ? "bg-card" : "bg-muted/40",
+                      isSelected && "outline-2 -outline-offset-2 outline-primary",
+                    )}
+                  >
                     <span
-                      className={`flex items-center gap-1 truncate rounded px-1 py-0.5 text-[0.7rem] ${EVENT_TONE[event.type]}`}
+                      className={cn(
+                        "flex items-center gap-1 text-xs",
+                        isCurrentMonth ? "text-foreground" : "text-muted-foreground",
+                        isToday && "font-semibold",
+                      )}
                     >
-                      <Icon className="size-3 shrink-0" />
-                      <span className="truncate">{event.title}</span>
+                      <span
+                        className={cn(
+                          "flex size-6 items-center justify-center rounded-full",
+                          isToday && "bg-primary text-primary-foreground",
+                        )}
+                      >
+                        {day.getDate()}
+                      </span>
+                      {isToday ? <span>Heute</span> : null}
                     </span>
-                  );
-                  return href ? (
-                    <Link key={event.id} href={href}>
-                      {content}
-                    </Link>
-                  ) : (
-                    <div key={event.id}>{content}</div>
-                  );
-                })}
-                {dayEvents.length > 3 ? (
-                  <span className="text-[0.7rem] text-muted-foreground">
-                    +{dayEvents.length - 3} weitere
-                  </span>
-                ) : null}
-              </div>
+                    <span className="flex flex-col gap-1">
+                      {dayEvents.slice(0, 3).map((event) => {
+                        const meta = EVENT_META[event.type];
+                        const Icon = meta.icon;
+                        return (
+                          <span
+                            key={event.id}
+                            className={cn(
+                              "flex items-center gap-1 truncate rounded px-1 py-0.5 text-xs",
+                              meta.tone,
+                            )}
+                          >
+                            <Icon className="size-3 shrink-0" aria-hidden />
+                            <span className="truncate">{event.title}</span>
+                          </span>
+                        );
+                      })}
+                      {dayEvents.length > 3 ? (
+                        <span className="text-xs text-muted-foreground">
+                          +{dayEvents.length - 3} weitere
+                        </span>
+                      ) : null}
+                    </span>
+                  </button>
+                );
+              })}
             </div>
-          );
-        })}
-      </div>
+            {selectedDay ? (
+              <DayEvents
+                date={selectedDay}
+                events={eventsByDay.get(selectedKey) ?? []}
+                isToday={selectedKey === todayKey}
+              />
+            ) : null}
+          </div>
+        </>
+      ) : null}
     </main>
   );
 }