diff --git a/library/core/src/time.rs b/library/core/src/time.rs
index 88fe29c9997..89202e7bb8d 100644
--- a/library/core/src/time.rs
+++ b/library/core/src/time.rs
@@ -1084,40 +1084,42 @@ pub fn div_f32(self, rhs: f32) -> Duration {
     ///
     /// # Examples
     /// ```
-    /// #![feature(div_duration)]
     /// use std::time::Duration;
     ///
     /// let dur1 = Duration::new(2, 700_000_000);
     /// let dur2 = Duration::new(5, 400_000_000);
     /// assert_eq!(dur1.div_duration_f64(dur2), 0.5);
     /// ```
-    #[unstable(feature = "div_duration", issue = "63139")]
+    #[stable(feature = "div_duration", since = "CURRENT_RUSTC_VERSION")]
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[inline]
     #[rustc_const_unstable(feature = "duration_consts_float", issue = "72440")]
     pub const fn div_duration_f64(self, rhs: Duration) -> f64 {
-        self.as_secs_f64() / rhs.as_secs_f64()
+        let self_nanos = (self.secs as f64) * (NANOS_PER_SEC as f64) + (self.nanos.0 as f64);
+        let rhs_nanos = (rhs.secs as f64) * (NANOS_PER_SEC as f64) + (rhs.nanos.0 as f64);
+        self_nanos / rhs_nanos
     }
 
     /// Divide `Duration` by `Duration` and return `f32`.
     ///
     /// # Examples
     /// ```
-    /// #![feature(div_duration)]
     /// use std::time::Duration;
     ///
     /// let dur1 = Duration::new(2, 700_000_000);
     /// let dur2 = Duration::new(5, 400_000_000);
     /// assert_eq!(dur1.div_duration_f32(dur2), 0.5);
     /// ```
-    #[unstable(feature = "div_duration", issue = "63139")]
+    #[stable(feature = "div_duration", since = "CURRENT_RUSTC_VERSION")]
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[inline]
     #[rustc_const_unstable(feature = "duration_consts_float", issue = "72440")]
     pub const fn div_duration_f32(self, rhs: Duration) -> f32 {
-        self.as_secs_f32() / rhs.as_secs_f32()
+        let self_nanos = (self.secs as f32) * (NANOS_PER_SEC as f32) + (self.nanos.0 as f32);
+        let rhs_nanos = (rhs.secs as f32) * (NANOS_PER_SEC as f32) + (rhs.nanos.0 as f32);
+        self_nanos / rhs_nanos
     }
 }
 
diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs
index e6828f6cb4e..e42cec304ef 100644
--- a/library/core/tests/lib.rs
+++ b/library/core/tests/lib.rs
@@ -29,7 +29,6 @@
 #![feature(core_private_bignum)]
 #![feature(core_private_diy_float)]
 #![feature(dec2flt)]
-#![feature(div_duration)]
 #![feature(duration_abs_diff)]
 #![feature(duration_consts_float)]
 #![feature(duration_constants)]