diff --git a/feature/mutual/src/main/java/com/rtbishop/look4sat/feature/mutual/MutualViewModel.kt b/feature/mutual/src/main/java/com/rtbishop/look4sat/feature/mutual/MutualViewModel.kt
index 0020d534..2188d90e 100644
--- a/feature/mutual/src/main/java/com/rtbishop/look4sat/feature/mutual/MutualViewModel.kt
+++ b/feature/mutual/src/main/java/com/rtbishop/look4sat/feature/mutual/MutualViewModel.kt
@@ -82,7 +82,10 @@ class MutualViewModel(
     private val settingsRepo: ISettingsRepo,
     // Injected so unit tests can run the pass computation on a test dispatcher;
     // production callers keep the CPU-bound pool default.
-    private val computeDispatcher: CoroutineDispatcher = Dispatchers.Default
+    private val computeDispatcher: CoroutineDispatcher = Dispatchers.Default,
+    // Injected so unit tests can pin the wall clock to the fixture TLE epoch and
+    // stay deterministic; production callers keep the real clock default.
+    private val nowMillis: () -> Long = System::currentTimeMillis
 ) : ViewModel() {
 
     private val _uiState = MutableStateFlow(MutualUiState())
@@ -303,7 +306,7 @@ class MutualViewModel(
         queryGeneration += 1
 
         viewModelScope.launch {
-            val now = System.currentTimeMillis()
+            val now = nowMillis()
             // 转发器类型筛选: 使用硬编码 AMSAT Live 清单 (见 Sources):
             // FM = {SO-50, ISS ZARYA, AO-123}, Linear = {RS-44, FO-29,
             // AO-7, AO-73, JO-97}. 不再依赖 AMSAT 网页同步: 任何网络下都
diff --git a/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/MutualViewModelTest.kt b/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/MutualViewModelTest.kt
index 8077b90c..d3942037 100644
--- a/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/MutualViewModelTest.kt
+++ b/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/MutualViewModelTest.kt
@@ -53,7 +53,9 @@ class MutualViewModelTest {
     ): MutualViewModel = MutualViewModel(
         satelliteRepo = FakeSatelliteRepo(satellites, passes),
         settingsRepo = FakeSettingsRepo(position),
-        computeDispatcher = StandardTestDispatcher(mainDispatcherRule.dispatcher.scheduler)
+        computeDispatcher = StandardTestDispatcher(mainDispatcherRule.dispatcher.scheduler),
+        // Pin the clock to the fixture base so results never depend on wall time.
+        nowMillis = { TestOrbits.FIXTURE_BASE }
     )
 
     private fun TestScope.queryAndSettle(vm: MutualViewModel) {
@@ -219,7 +221,7 @@ class MutualViewModelTest {
         assertTrue(state.mutualPasses.all { it.catNum == 25544 })
         assertTrue(state.mutualPasses.all { it.name == "ISS (ZARYA)" })
         // AOS/LOS within the searched horizon
-        val now = System.currentTimeMillis()
+        val now = TestOrbits.FIXTURE_BASE
         assertTrue(state.mutualPasses.all { it.startTime >= now - 120_000L })
         assertTrue(state.mutualPasses.all { it.endTime <= now + 12 * 3600_000L + 120_000L })
     }
diff --git a/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/TestOrbits.kt b/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/TestOrbits.kt
index 8acce29a..743bd1f0 100644
--- a/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/TestOrbits.kt
+++ b/feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/TestOrbits.kt
@@ -48,6 +48,15 @@ object TestOrbits {
         )
     )
 
+    /**
+     * Fixed wall-clock base for every fixture computation: 2024-03-10T00:00Z,
+     * ~18 h after [ISS]'s TLE epoch, so SGP4 propagates an accurate, healthy
+     * orbit. Tests pin the ViewModel clock to this value as well
+     * (MutualViewModel.nowMillis), which makes pass windows deterministic
+     * instead of rotting as the fixture ages against System.currentTimeMillis().
+     */
+    val FIXTURE_BASE: Long = 1710028800000L
+
     /** Guangzhou (default BA7OPF grid OL62/OL63 area). */
     val GUANGZHOU = GeoPos(23.13, 113.26)
 
@@ -85,7 +94,7 @@ object TestOrbits {
     fun findPassWindows(
         sat: OrbitalObject = ISS,
         pos: GeoPos = GUANGZHOU,
-        time: Long = System.currentTimeMillis(),
+        time: Long = FIXTURE_BASE,
         hoursAhead: Int = 12
     ): List<OrbitalPass> {
         if (!sat.willBeSeen(pos)) return emptyList()