diff --git a/src/time_system.nvgt b/src/time_system.nvgt
index 2825c86..7235668 100644
--- a/src/time_system.nvgt
+++ b/src/time_system.nvgt
@@ -354,6 +354,18 @@ int get_random_invasion_hour(int min_hour) {
     return random(min_hour, 11);
 }
 
+bool is_night_hour(int hour) {
+    return hour < 6 || hour >= 19;
+}
+
+int get_random_zombie_swarm_hour(int min_hour) {
+    if (!is_night_hour(min_hour)) return -1;
+    if (min_hour >= 19) {
+        return random(min_hour, 23);
+    }
+    return random(min_hour, 5);
+}
+
 void schedule_invasion() {
     if (invasion_scheduled_hour != -1) return;
     int hour = get_random_invasion_hour(current_hour);
@@ -432,6 +444,10 @@ void end_zombie_swarm() {
 
 void check_zombie_swarm_status() {
     if (!zombie_swarm_active) return;
+    if (!is_night_hour(current_hour)) {
+        end_zombie_swarm();
+        return;
+    }
     int hours_elapsed = current_hour - zombie_swarm_start_hour;
     if (hours_elapsed < 0) {
         hours_elapsed += 24;
@@ -443,7 +459,7 @@ void check_zombie_swarm_status() {
 
 void schedule_zombie_swarm() {
     if (zombie_swarm_scheduled_hour != -1) return;
-    int hour = get_random_invasion_hour(current_hour);
+    int hour = get_random_zombie_swarm_hour(current_hour);
     if (hour == -1) return;
     zombie_swarm_scheduled_hour = hour;
 }
@@ -451,12 +467,14 @@ void schedule_zombie_swarm() {
 void check_scheduled_zombie_swarm() {
     if (zombie_swarm_active) return;
     if (zombie_swarm_scheduled_hour != -1) {
+        if (!is_night_hour(zombie_swarm_scheduled_hour) || !is_night_hour(current_hour)) {
+            zombie_swarm_scheduled_hour = -1;
+            return;
+        }
         if (current_hour == zombie_swarm_scheduled_hour) {
             zombie_swarm_scheduled_hour = -1;
             zombie_swarm_triggered_today = true;
             start_zombie_swarm();
-        } else if (current_hour > 11) {
-            zombie_swarm_scheduled_hour = -1;
         }
         return;
     }
@@ -466,7 +484,7 @@ void check_scheduled_zombie_swarm() {
 void attempt_daily_zombie_swarm() {
     if (!can_roll_zombie_swarm_today()) return;
     if (zombie_swarm_roll_done_today || zombie_swarm_triggered_today || zombie_swarm_active) return;
-    if (current_hour < 6) return;
+    if (!is_night_hour(current_hour)) return;
 
     zombie_swarm_roll_done_today = true;
     int chance = get_zombie_swarm_chance_for_day();