diff --git a/SportsTimeTests/ScenarioAPlannerSwiftTests.swift b/SportsTimeTests/ScenarioAPlannerSwiftTests.swift
index 842ae05..959aa5b 100644
--- a/SportsTimeTests/ScenarioAPlannerSwiftTests.swift
+++ b/SportsTimeTests/ScenarioAPlannerSwiftTests.swift
@@ -669,4 +669,202 @@ struct ScenarioAPlannerSwiftTests {
             #expect(option.isValid)
         }
     }
+
+    // MARK: - Timezone Boundary Tests
+
+    @Test("game at range start in different timezone is included")
+    func plan_GameAtRangeStartDifferentTimezone_Included() {
+        // Date range: Jan 5 00:00 PST to Jan 10 23:59 PST
+        let pstCalendar = Calendar.current
+        var pstComponents = DateComponents()
+        pstComponents.year = 2026
+        pstComponents.month = 1
+        pstComponents.day = 5
+        pstComponents.hour = 0
+        pstComponents.minute = 0
+        pstComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeStart = pstCalendar.date(from: pstComponents)!
+
+        var endComponents = DateComponents()
+        endComponents.year = 2026
+        endComponents.month = 1
+        endComponents.day = 10
+        endComponents.hour = 23
+        endComponents.minute = 59
+        endComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeEnd = pstCalendar.date(from: endComponents)!
+
+        let dateRange = DateInterval(start: rangeStart, end: rangeEnd)
+
+        // Game: Jan 5 19:00 EST (New York) = Jan 5 16:00 PST
+        let nyStadium = makeStadium(city: "New York", latitude: 40.7128, longitude: -74.0060)
+
+        var estComponents = DateComponents()
+        estComponents.year = 2026
+        estComponents.month = 1
+        estComponents.day = 5
+        estComponents.hour = 19
+        estComponents.minute = 0
+        estComponents.timeZone = TimeZone(identifier: "America/New_York")!
+        let gameTime = pstCalendar.date(from: estComponents)!
+
+        let game = makeGame(stadiumId: nyStadium.id, dateTime: gameTime)
+
+        let result = plan(
+            games: [game],
+            stadiums: [nyStadium],
+            dateRange: dateRange
+        )
+
+        // Game should be included (within PST range)
+        #expect(result.isSuccess)
+        #expect(result.options.first?.stops.count == 1)
+    }
+
+    @Test("game just before range start in different timezone is excluded")
+    func plan_GameBeforeRangeStartDifferentTimezone_Excluded() {
+        // Date range: Jan 5 00:00 PST to Jan 10 23:59 PST
+        let pstCalendar = Calendar.current
+        var pstComponents = DateComponents()
+        pstComponents.year = 2026
+        pstComponents.month = 1
+        pstComponents.day = 5
+        pstComponents.hour = 0
+        pstComponents.minute = 0
+        pstComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeStart = pstCalendar.date(from: pstComponents)!
+
+        var endComponents = DateComponents()
+        endComponents.year = 2026
+        endComponents.month = 1
+        endComponents.day = 10
+        endComponents.hour = 23
+        endComponents.minute = 59
+        endComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeEnd = pstCalendar.date(from: endComponents)!
+
+        let dateRange = DateInterval(start: rangeStart, end: rangeEnd)
+
+        // Game: Jan 4 22:00 EST (New York) = Jan 4 19:00 PST
+        let nyStadium = makeStadium(city: "New York", latitude: 40.7128, longitude: -74.0060)
+
+        var estComponents = DateComponents()
+        estComponents.year = 2026
+        estComponents.month = 1
+        estComponents.day = 4
+        estComponents.hour = 22
+        estComponents.minute = 0
+        estComponents.timeZone = TimeZone(identifier: "America/New_York")!
+        let gameTime = pstCalendar.date(from: estComponents)!
+
+        let game = makeGame(stadiumId: nyStadium.id, dateTime: gameTime)
+
+        let result = plan(
+            games: [game],
+            stadiums: [nyStadium],
+            dateRange: dateRange
+        )
+
+        // Game should be excluded (before PST range start)
+        #expect(result.failure?.reason == .noGamesInRange)
+    }
+
+    @Test("game at range end in different timezone is included")
+    func plan_GameAtRangeEndDifferentTimezone_Included() {
+        // Date range: Jan 5 00:00 PST to Jan 10 23:59 PST
+        let pstCalendar = Calendar.current
+        var pstComponents = DateComponents()
+        pstComponents.year = 2026
+        pstComponents.month = 1
+        pstComponents.day = 5
+        pstComponents.hour = 0
+        pstComponents.minute = 0
+        pstComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeStart = pstCalendar.date(from: pstComponents)!
+
+        var endComponents = DateComponents()
+        endComponents.year = 2026
+        endComponents.month = 1
+        endComponents.day = 10
+        endComponents.hour = 23
+        endComponents.minute = 59
+        endComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeEnd = pstCalendar.date(from: endComponents)!
+
+        let dateRange = DateInterval(start: rangeStart, end: rangeEnd)
+
+        // Game: Jan 10 21:00 EST (New York) = Jan 10 18:00 PST
+        let nyStadium = makeStadium(city: "New York", latitude: 40.7128, longitude: -74.0060)
+
+        var estComponents = DateComponents()
+        estComponents.year = 2026
+        estComponents.month = 1
+        estComponents.day = 10
+        estComponents.hour = 21
+        estComponents.minute = 0
+        estComponents.timeZone = TimeZone(identifier: "America/New_York")!
+        let gameTime = pstCalendar.date(from: estComponents)!
+
+        let game = makeGame(stadiumId: nyStadium.id, dateTime: gameTime)
+
+        let result = plan(
+            games: [game],
+            stadiums: [nyStadium],
+            dateRange: dateRange
+        )
+
+        // Game should be included (within PST range)
+        #expect(result.isSuccess)
+        #expect(result.options.first?.stops.count == 1)
+    }
+
+    @Test("game just after range end in different timezone is excluded")
+    func plan_GameAfterRangeEndDifferentTimezone_Excluded() {
+        // Date range: Jan 5 00:00 PST to Jan 10 23:59 PST
+        let pstCalendar = Calendar.current
+        var pstComponents = DateComponents()
+        pstComponents.year = 2026
+        pstComponents.month = 1
+        pstComponents.day = 5
+        pstComponents.hour = 0
+        pstComponents.minute = 0
+        pstComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeStart = pstCalendar.date(from: pstComponents)!
+
+        var endComponents = DateComponents()
+        endComponents.year = 2026
+        endComponents.month = 1
+        endComponents.day = 10
+        endComponents.hour = 23
+        endComponents.minute = 59
+        endComponents.timeZone = TimeZone(identifier: "America/Los_Angeles")!
+        let rangeEnd = pstCalendar.date(from: endComponents)!
+
+        let dateRange = DateInterval(start: rangeStart, end: rangeEnd)
+
+        // Game: Jan 11 02:00 EST (New York) = Jan 10 23:00 PST
+        // This is actually WITHIN the range (before 23:59 PST)
+        // Let me adjust: Jan 11 03:00 EST = Jan 11 00:00 PST (after range)
+        let nyStadium = makeStadium(city: "New York", latitude: 40.7128, longitude: -74.0060)
+
+        var estComponents = DateComponents()
+        estComponents.year = 2026
+        estComponents.month = 1
+        estComponents.day = 11
+        estComponents.hour = 3
+        estComponents.minute = 0
+        estComponents.timeZone = TimeZone(identifier: "America/New_York")!
+        let gameTime = pstCalendar.date(from: estComponents)!
+
+        let game = makeGame(stadiumId: nyStadium.id, dateTime: gameTime)
+
+        let result = plan(
+            games: [game],
+            stadiums: [nyStadium],
+            dateRange: dateRange
+        )
+
+        // Game should be excluded (after PST range end)
+        #expect(result.failure?.reason == .noGamesInRange)
+    }
 }