diff --git a/library/core/src/time.rs b/library/core/src/time.rs
index 7db03367fd53..d7fa5f9bf0a7 100644
--- a/library/core/src/time.rs
+++ b/library/core/src/time.rs
@@ -136,16 +136,18 @@ impl Duration {
 
     /// The maximum duration.
     ///
-    /// It is roughly equal to a duration of 584,942,417,355 years.
+    /// May vary by platform. At least equal to the number of seconds
+    /// difference between the minimum and maximum [`std::time::Instant`].
+    /// On many platforms this is roughly 584,942,417,355 years.
     ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(duration_constants)]
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::MAX, Duration::new(u64::MAX, 1_000_000_000 - 1));
     /// ```
+    /// [`std::time::Instant`]: ../../std/time/struct.Instant.html
     #[stable(feature = "duration_saturating_ops", since = "1.53.0")]
     pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);