diff --git a/packages/playwright-core/src/client/clock.ts b/packages/playwright-core/src/client/clock.ts
index 32faa7a4d4f2e..73eb538c264bf 100644
--- a/packages/playwright-core/src/client/clock.ts
+++ b/packages/playwright-core/src/client/clock.ts
@@ -58,6 +58,8 @@ function parseTime(time: string | number | Date): { timeNumber?: number, timeStr
     return { timeNumber: time };
   if (typeof time === 'string')
     return { timeString: time };
+  if (!isFinite(time.getTime()))
+    throw new Error(`Invalid date: ${time}`);
   return { timeNumber: time.getTime() };
 }
 
diff --git a/packages/playwright-core/src/server/clock.ts b/packages/playwright-core/src/server/clock.ts
index 1e0822ff04b2d..5049e4766d9f3 100644
--- a/packages/playwright-core/src/server/clock.ts
+++ b/packages/playwright-core/src/server/clock.ts
@@ -148,5 +148,8 @@ function parseTime(epoch: string | number | undefined): number {
     return 0;
   if (typeof epoch === 'number')
     return epoch;
-  return new Date(epoch).getTime();
+  const parsed = new Date(epoch);
+  if (!isFinite(parsed.getTime()))
+    throw new Error(`Invalid date: ${epoch}`);
+  return parsed.getTime();
 }
diff --git a/tests/page/page-clock.spec.ts b/tests/page/page-clock.spec.ts
index 670891a40a229..29854c969c9b9 100644
--- a/tests/page/page-clock.spec.ts
+++ b/tests/page/page-clock.spec.ts
@@ -245,6 +245,11 @@ it.describe('stubTimers', () => {
     expect(await page.evaluate(() => Date.now())).toBe(1400);
   });
 
+  it('should throw for invalid date', async ({ page }) => {
+    await expect(page.clock.setSystemTime(new Date('invalid'))).rejects.toThrow('Invalid date: Invalid Date');
+    await expect(page.clock.setSystemTime('invalid')).rejects.toThrow('clock.setSystemTime: Invalid date: invalid');
+  });
+
   it('replaces global setTimeout', async ({ page, calls }) => {
     await page.evaluate(async () => {
       setTimeout(window.stub, 1000);