diff --git a/container/agent-runner/src/ipc-mcp-stdio.ts b/container/agent-runner/src/ipc-mcp-stdio.ts
index d894fe8..006b812 100644
--- a/container/agent-runner/src/ipc-mcp-stdio.ts
+++ b/container/agent-runner/src/ipc-mcp-stdio.ts
@@ -112,10 +112,16 @@ SCHEDULE VALUE FORMAT (all times are LOCAL timezone):
         };
       }
     } else if (args.schedule_type === 'once') {
+      if (/[Zz]$/.test(args.schedule_value) || /[+-]\d{2}:\d{2}$/.test(args.schedule_value)) {
+        return {
+          content: [{ type: 'text' as const, text: `Timestamp must be local time without timezone suffix. Got "${args.schedule_value}" — use format like "2026-02-01T15:30:00".` }],
+          isError: true,
+        };
+      }
       const date = new Date(args.schedule_value);
       if (isNaN(date.getTime())) {
         return {
-          content: [{ type: 'text' as const, text: `Invalid timestamp: "${args.schedule_value}". Use ISO 8601 format like "2026-02-01T15:30:00.000Z".` }],
+          content: [{ type: 'text' as const, text: `Invalid timestamp: "${args.schedule_value}". Use local time format like "2026-02-01T15:30:00".` }],
           isError: true,
         };
       }
diff --git a/src/container-runner.test.ts b/src/container-runner.test.ts
index 99c1cc7..1875c3f 100644
--- a/src/container-runner.test.ts
+++ b/src/container-runner.test.ts
@@ -14,6 +14,7 @@ vi.mock('./config.js', () => ({
   DATA_DIR: '/tmp/nanoclaw-test-data',
   GROUPS_DIR: '/tmp/nanoclaw-test-groups',
   IDLE_TIMEOUT: 1800000, // 30min
+  TIMEZONE: 'America/Los_Angeles',
 }));
 
 // Mock logger
diff --git a/src/container-runner.ts b/src/container-runner.ts
index ffb6920..acfbe00 100644
--- a/src/container-runner.ts
+++ b/src/container-runner.ts
@@ -13,6 +13,7 @@ import {
   DATA_DIR,
   GROUPS_DIR,
   IDLE_TIMEOUT,
+  TIMEZONE,
 } from './config.js';
 import { readEnvFile } from './env.js';
 import { resolveGroupFolderPath, resolveGroupIpcPath } from './group-folder.js';
@@ -187,6 +188,9 @@ function readSecrets(): Record<string, string> {
 function buildContainerArgs(mounts: VolumeMount[], containerName: string): string[] {
   const args: string[] = ['run', '-i', '--rm', '--name', containerName];
 
+  // Pass host timezone so container's local time matches the user's
+  args.push('-e', `TZ=${TIMEZONE}`);
+
   // Run as host user so bind-mounted files are accessible.
   // Skip when running as root (uid 0), as the container's node user (uid 1000),
   // or when getuid is unavailable (native Windows without WSL).