diff --git a/docs/gateway/heartbeat.md b/docs/gateway/heartbeat.md
index 9cfeea19a3d..b682da0f814 100644
--- a/docs/gateway/heartbeat.md
+++ b/docs/gateway/heartbeat.md
@@ -167,7 +167,7 @@ Outside this window (before 9am or after 10pm Eastern), heartbeats are skipped.
 
 If you want heartbeats to run all day, use one of these patterns:
 
-- Omit `activeHours` entirely (no time-window restriction).
+- Omit `activeHours` entirely (no time-window restriction; this is the default behavior).
 - Set a full-day window: `activeHours: { start: "00:00", end: "24:00" }`.
 
 Do not set the same `start` and `end` time (for example `08:00` to `08:00`).
@@ -220,7 +220,7 @@ Use `accountId` to target a specific account on multi-account channels like Tele
 - `prompt`: overrides the default prompt body (not merged).
 - `ackMaxChars`: max chars allowed after `HEARTBEAT_OK` before delivery.
 - `suppressToolErrorWarnings`: when true, suppresses tool error warning payloads during heartbeat runs.
-- `activeHours`: restricts heartbeat runs to a time window. Object with `start` (HH:MM, inclusive), `end` (HH:MM exclusive; `24:00` allowed for end-of-day), and optional `timezone`.
+- `activeHours`: restricts heartbeat runs to a time window. Object with `start` (HH:MM, inclusive; use `00:00` for start-of-day), `end` (HH:MM exclusive; `24:00` allowed for end-of-day), and optional `timezone`.
   - Omitted or `"user"`: uses your `agents.defaults.userTimezone` if set, otherwise falls back to the host system timezone.
   - `"local"`: always uses the host system timezone.
   - Any IANA identifier (e.g. `America/New_York`): used directly; if invalid, falls back to the `"user"` behavior above.