diff --git a/lib/booking/day_schedule.rb b/lib/booking/day_schedule.rb
index d991f8a..0bf21f8 100644
--- a/lib/booking/day_schedule.rb
+++ b/lib/booking/day_schedule.rb
@@ -2,11 +2,13 @@ module Booking
   class DaySchedule
     CannotReserve = Class.new(StandardError)
 
-    def initialize
+    def initialize(allowed_time_range)
       @reserved_slots = Set.new
+      @allowed_time_range = allowed_time_range
     end
 
     def reserve(time_range)
+      cannot_reserve unless allowed_time_range.cover?(time_range)
       cannot_reserve if reserved_slots.any?(covers?(time_range))
       reserved_slots << time_range
       visit_scheduled(time_range)
@@ -14,13 +16,15 @@ def reserve(time_range)
 
     private
 
-    attr_reader :reserved_slots
+    attr_reader :reserved_slots, :allowed_time_range
 
     def visit_scheduled(time_range)
-      VisitScheduled.new(data: {
-        scheduled_at: time_range.first,
-        duration: time_range.last - time_range.first
-      })
+      VisitScheduled.new(
+        data: {
+          scheduled_at: time_range.first,
+          duration: time_range.last - time_range.first
+        }
+      )
     end
 
     def covers?(time_range)
@@ -31,4 +35,4 @@ def cannot_reserve
       raise CannotReserve
     end
   end
-end
\ No newline at end of file
+end
diff --git a/test/lib/booking/day_schedule_test.rb b/test/lib/booking/day_schedule_test.rb
index 4a4b9f6..5bcf1ae 100644
--- a/test/lib/booking/day_schedule_test.rb
+++ b/test/lib/booking/day_schedule_test.rb
@@ -5,14 +5,14 @@ class DayScheduleTest < ActiveSupport::TestCase
     cover DaySchedule
 
     test "happy path" do
-      day_schedule = DaySchedule.new
+      day_schedule = DaySchedule.new(open_hours)
 
       assert_event visit_scheduled(at_12_00..at_13_00),
                    day_schedule.reserve(at_12_00..at_13_00)
     end
 
     test "cannot reserve same slot twice" do
-      day_schedule = DaySchedule.new
+      day_schedule = DaySchedule.new(open_hours)
       day_schedule.reserve(at_12_00..at_13_00)
 
       assert_raises DaySchedule::CannotReserve do
@@ -21,7 +21,7 @@ class DayScheduleTest < ActiveSupport::TestCase
     end
 
     test "cannot reserve partially covered slot" do
-      day_schedule = DaySchedule.new
+      day_schedule = DaySchedule.new(open_hours)
       day_schedule.reserve(at_12_00..at_13_00)
 
       assert_raises DaySchedule::CannotReserve do
@@ -30,7 +30,7 @@ class DayScheduleTest < ActiveSupport::TestCase
     end
 
     test "cannot reserve partially covered slot, again" do
-      day_schedule = DaySchedule.new
+      day_schedule = DaySchedule.new(open_hours)
       day_schedule.reserve(at_12_00..at_13_00)
 
       assert_raises DaySchedule::CannotReserve do
@@ -39,15 +39,26 @@ class DayScheduleTest < ActiveSupport::TestCase
     end
 
     test "can reserve non-intersecting slots" do
-      day_schedule = DaySchedule.new
+      day_schedule = DaySchedule.new(open_hours)
       day_schedule.reserve(at_12_00..at_12_45)
 
       assert_event visit_scheduled(at_13_00..at_13_45),
                    day_schedule.reserve(at_13_00..at_13_45)
     end
 
+    test "cannot reserve outside of open hours" do
+      day_schedule = DaySchedule.new(open_hours)
+      open_at, close_at = open_hours.first, open_hours.last
+
+      assert_raises { day_schedule.reserve(open_at..(close_at + 1.hour)) }
+    end
+
     private
 
+    def open_hours
+      at_11_00..at_19_00
+    end
+
     def visit_scheduled(time_range)
       VisitScheduled.new(
         data: {
@@ -57,6 +68,10 @@ def visit_scheduled(time_range)
       )
     end
 
+    def at_11_00
+      Time.new(2023, 10, 10, 11, 00)
+    end
+
     def at_11_45
       Time.new(2023, 10, 10, 11, 45)
     end
@@ -76,5 +91,9 @@ def at_13_00
     def at_13_45
       Time.new(2023, 10, 10, 13, 45)
     end
+
+    def at_19_00
+      Time.new(2023, 10, 10, 19, 00)
+    end
   end
-end
\ No newline at end of file
+end