diff --git a/src/sources/live/aircraft.js b/src/sources/live/aircraft.js
index 0c7614021..6b05ac528 100644
--- a/src/sources/live/aircraft.js
+++ b/src/sources/live/aircraft.js
@@ -141,7 +141,8 @@ export function normalizeAircraftTrack(
     const latitude = finite(row[1]),
       longitude = finite(row[2]);
     const offset = finite(row[0]);
-    const observedAtMs = offset == null ? null : baseTimeMs + offset * 1000;
+    const observedAtMs =
+      offset == null ? null : epoch(baseTimeMs + offset * 1000);
     if (
       !coordinates(latitude, longitude) ||
       observedAtMs == null ||
diff --git a/src/sources/live/contract.js b/src/sources/live/contract.js
index a1169f1f2..2415ff43c 100644
--- a/src/sources/live/contract.js
+++ b/src/sources/live/contract.js
@@ -32,7 +32,12 @@ export function finite(value) {
 
 export function epoch(value, scale = 1) {
   const number = finite(value);
-  return number != null && number > 0 ? number * scale : null;
+  const milliseconds = number == null ? null : number * scale;
+  return milliseconds != null &&
+    milliseconds > 0 &&
+    milliseconds <= 8640000000000000
+    ? milliseconds
+    : null;
 }
 
 export function cleanText(value) {
diff --git a/src/sources/live/contract.test.mjs b/src/sources/live/contract.test.mjs
index 6ddf51a5d..76cbae24c 100644
--- a/src/sources/live/contract.test.mjs
+++ b/src/sources/live/contract.test.mjs
@@ -261,3 +261,13 @@ test('a malformed vessel row cannot prevent admission of valid positions', async
   assert.equal(snapshot.rejectedCount, 1);
   assert.equal(snapshot.complete, false);
 });
+
+test('out-of-range source epochs do not reach Date or globe time constructors', () => {
+  const row = [...aircraft];
+  row[3] = 1e100;
+  row[4] = 1e100;
+  const snapshot = openSkySnapshot({ time: 1e100, states: [row] });
+  assert.equal(snapshot.observedAtMs, null);
+  assert.equal(snapshot.records[0].positionTimeMs, null);
+  assert.equal(snapshot.records[0].contactTimeMs, null);
+});