diff --git a/crates/bevy_time/src/stopwatch.rs b/crates/bevy_time/src/stopwatch.rs
index 632d4c1764e11..7579b3a8b6f01 100644
--- a/crates/bevy_time/src/stopwatch.rs
+++ b/crates/bevy_time/src/stopwatch.rs
@@ -4,6 +4,7 @@ use bevy_utils::Duration;
 
 /// A Stopwatch is a struct that track elapsed time when started.
 ///
+/// Note that in order to advance the stopwatch [`tick`](Stopwatch::tick) **MUST** be called.
 /// # Examples
 ///
 /// ```
diff --git a/crates/bevy_time/src/timer.rs b/crates/bevy_time/src/timer.rs
index 7995f986a4d8c..c594a73140e33 100644
--- a/crates/bevy_time/src/timer.rs
+++ b/crates/bevy_time/src/timer.rs
@@ -10,6 +10,8 @@ use bevy_utils::Duration;
 /// exceeded, and can still be reset at any given point.
 ///
 /// Paused timers will not have elapsed time increased.
+///
+/// Note that in order to advance the timer [`tick`](Timer::tick) **MUST** be called.
 #[derive(Clone, Debug, Default, PartialEq, Eq)]
 #[cfg_attr(feature = "serialize", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "bevy_reflect", derive(Reflect), reflect(Default))]