diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6491629f542..00cdbfab5fb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ Docs: https://docs.openclaw.ai
 ### Fixes
 
 - Heartbeat/Cron: restore interval heartbeat behavior so missing `HEARTBEAT.md` no longer suppresses runs (only effectively empty files skip), preserving prompt-driven and tagged-cron execution paths.
+- Heartbeat/Active hours: constrain active-hours `24` sentinel parsing to `24:00` in time validation so invalid values like `24:30` are rejected early. (#21410) thanks @adhitShet.
 - Gateway/Pairing: tolerate legacy paired devices missing `roles`/`scopes` metadata in websocket upgrade checks and backfill metadata on reconnect. (#21447, fixes #21236) Thanks @joshavant.
 - Docker: pin base images to SHA256 digests in Docker builds to prevent mutable tag drift. (#7734) Thanks @coygeek.
 - Provider/HTTP: treat HTTP 503 as failover-eligible for LLM provider errors. (#21086) Thanks @Protocol-zero-0.
diff --git a/src/infra/heartbeat-active-hours.ts b/src/infra/heartbeat-active-hours.ts
index 1d9f1d3362d..91341b69a8b 100644
--- a/src/infra/heartbeat-active-hours.ts
+++ b/src/infra/heartbeat-active-hours.ts
@@ -4,7 +4,7 @@ import type { AgentDefaultsConfig } from "../config/types.agent-defaults.js";
 
 type HeartbeatConfig = AgentDefaultsConfig["heartbeat"];
 
-const ACTIVE_HOURS_TIME_PATTERN = /^([01]\d|2[0-3]|24):([0-5]\d)$/;
+const ACTIVE_HOURS_TIME_PATTERN = /^(?:([01]\d|2[0-3]):([0-5]\d)|24:00)$/;
 
 function resolveActiveHoursTimezone(cfg: OpenClawConfig, raw?: string): string {
   const trimmed = raw?.trim();