diff --git a/backend/src/main/java/es/asepeyo/recordalexia/service/TodayService.java b/backend/src/main/java/es/asepeyo/recordalexia/service/TodayService.java
index 5743889..8c2b050 100644
--- a/backend/src/main/java/es/asepeyo/recordalexia/service/TodayService.java
+++ b/backend/src/main/java/es/asepeyo/recordalexia/service/TodayService.java
@@ -76,7 +76,7 @@ public class TodayService {
             events,
             ProgressCalculator.from(tasks),
             new WalletInfo(child.getCoins()),
-            buildTimer(child));
+            buildTimer(child.getDepartureTime(), LocalTime.now(clock), morning.isEmpty()));
     }
 
     private TaskView toTaskView(DailyTask t) {
@@ -95,13 +95,20 @@ public class TodayService {
             c.isDyslexiaFont());
     }
 
-    /** Temporizador de salida: minutos que faltan hasta departureTime (>= 0). */
-    private TimerInfo buildTimer(Child child) {
-        LocalTime departure = child.getDepartureTime();
-        if (departure == null) {
+    /**
+     * Temporizador de salida. Solo tiene sentido si HOY hay cole (hay tareas de
+     * mañana) y aún no ha pasado la hora: pasado ese momento desaparece, en vez de
+     * quedarse clavado en "0 min" el resto del día (o en domingo). Con minutos a
+     * null el kiosko no lo pinta.
+     */
+    static TimerInfo buildTimer(LocalTime departure, LocalTime now, boolean sinColeHoy) {
+        if (departure == null || sinColeHoy) {
             return new TimerInfo(null, null);
         }
-        long minutes = Duration.between(LocalTime.now(clock), departure).toMinutes();
-        return new TimerInfo(departure.format(HHMM), (int) Math.max(0, minutes));
+        long minutes = Duration.between(now, departure).toMinutes();
+        if (minutes < 0) {
+            return new TimerInfo(departure.format(HHMM), null);
+        }
+        return new TimerInfo(departure.format(HHMM), (int) minutes);
     }
 }
diff --git a/backend/src/test/java/es/asepeyo/recordalexia/service/TodayServiceTimerTest.java b/backend/src/test/java/es/asepeyo/recordalexia/service/TodayServiceTimerTest.java
new file mode 100644
index 0000000..d204c7f
--- /dev/null
+++ b/backend/src/test/java/es/asepeyo/recordalexia/service/TodayServiceTimerTest.java
@@ -0,0 +1,48 @@
+package es.asepeyo.recordalexia.service;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import es.asepeyo.recordalexia.web.dto.TodayResponse.TimerInfo;
+import java.time.LocalTime;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Reglas del temporizador "SALIMOS EN X min": solo aparece si hoy hay cole y la
+ * hora de salida no ha pasado; nunca se queda clavado en "0 min" el resto del día.
+ */
+class TodayServiceTimerTest {
+
+    private static final LocalTime SALIDA = LocalTime.of(8, 30);
+
+    @Test
+    void sinHoraDeSalidaNoHayTemporizador() {
+        TimerInfo timer = TodayService.buildTimer(null, LocalTime.of(8, 0), false);
+        assertThat(timer.departureTime()).isNull();
+        assertThat(timer.minutesUntilDeparture()).isNull();
+    }
+
+    @Test
+    void sinColeHoyNoHayTemporizador() {
+        TimerInfo timer = TodayService.buildTimer(SALIDA, LocalTime.of(8, 0), true);
+        assertThat(timer.minutesUntilDeparture()).isNull();
+    }
+
+    @Test
+    void antesDeLaHoraMuestraLosMinutosQueFaltan() {
+        TimerInfo timer = TodayService.buildTimer(SALIDA, LocalTime.of(8, 10), false);
+        assertThat(timer.departureTime()).isEqualTo("08:30");
+        assertThat(timer.minutesUntilDeparture()).isEqualTo(20);
+    }
+
+    @Test
+    void justoALaHoraMuestraCero() {
+        TimerInfo timer = TodayService.buildTimer(SALIDA, LocalTime.of(8, 30), false);
+        assertThat(timer.minutesUntilDeparture()).isZero();
+    }
+
+    @Test
+    void pasadaLaHoraDesaparece() {
+        TimerInfo timer = TodayService.buildTimer(SALIDA, LocalTime.of(10, 0), false);
+        assertThat(timer.minutesUntilDeparture()).isNull();
+    }
+}