diff --git a/src/naive/datetime/mod.rs b/src/naive/datetime/mod.rs
index b2f7d63bf0..d42c757bea 100644
--- a/src/naive/datetime/mod.rs
+++ b/src/naive/datetime/mod.rs
@@ -1460,11 +1460,11 @@ impl Timelike for NaiveDateTime {
     /// ```
     /// use chrono::{NaiveDate, NaiveDateTime, Timelike};
     ///
-    /// let dt: NaiveDateTime = NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_milli_opt(12, 34, 56, 789).unwrap();
+    /// let dt: NaiveDateTime = NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_milli_opt(12, 34, 59, 789).unwrap();
     /// assert_eq!(dt.with_nanosecond(333_333_333),
-    ///            Some(NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_nano_opt(12, 34, 56, 333_333_333).unwrap()));
+    ///            Some(NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_nano_opt(12, 34, 59, 333_333_333).unwrap()));
     /// assert_eq!(dt.with_nanosecond(1_333_333_333), // leap second
-    ///            Some(NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_nano_opt(12, 34, 56, 1_333_333_333).unwrap()));
+    ///            Some(NaiveDate::from_ymd_opt(2015, 9, 8).unwrap().and_hms_nano_opt(12, 34, 59, 1_333_333_333).unwrap()));
     /// assert_eq!(dt.with_nanosecond(2_000_000_000), None);
     /// ```
     #[inline]
diff --git a/src/naive/time/mod.rs b/src/naive/time/mod.rs
index 9fa4b8929a..e9e2e02970 100644
--- a/src/naive/time/mod.rs
+++ b/src/naive/time/mod.rs
@@ -1022,9 +1022,9 @@ impl Timelike for NaiveTime {
     ///
     /// ```
     /// # use chrono::{NaiveTime, Timelike};
-    /// # let dt = NaiveTime::from_hms_nano_opt(23, 56, 4, 12_345_678).unwrap();
-    /// assert_eq!(dt.with_nanosecond(1_333_333_333),
-    ///            Some(NaiveTime::from_hms_nano_opt(23, 56, 4, 1_333_333_333).unwrap()));
+    /// let dt = NaiveTime::from_hms_nano_opt(23, 56, 4, 12_345_678).unwrap();
+    /// let strange_leap_second = dt.with_nanosecond(1_333_333_333).unwrap();
+    /// assert_eq!(strange_leap_second.nanosecond(), 1_333_333_333);
     /// ```
     #[inline]
     fn with_nanosecond(&self, nano: u32) -> Option<NaiveTime> {
diff --git a/src/naive/time/tests.rs b/src/naive/time/tests.rs
index b77ca87339..f7a6ef5f92 100644
--- a/src/naive/time/tests.rs
+++ b/src/naive/time/tests.rs
@@ -13,12 +13,12 @@ fn test_time_from_hms_milli() {
         Some(NaiveTime::from_hms_nano_opt(3, 5, 7, 777_000_000).unwrap())
     );
     assert_eq!(
-        NaiveTime::from_hms_milli_opt(3, 5, 7, 1_999),
-        Some(NaiveTime::from_hms_nano_opt(3, 5, 7, 1_999_000_000).unwrap())
+        NaiveTime::from_hms_milli_opt(3, 5, 59, 1_999),
+        Some(NaiveTime::from_hms_nano_opt(3, 5, 59, 1_999_000_000).unwrap())
     );
-    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 7, 2_000), None);
-    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 7, 5_000), None); // overflow check
-    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 7, u32::MAX), None);
+    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 59, 2_000), None);
+    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 59, 5_000), None); // overflow check
+    assert_eq!(NaiveTime::from_hms_milli_opt(3, 5, 59, u32::MAX), None);
 }
 
 #[test]
@@ -36,12 +36,12 @@ fn test_time_from_hms_micro() {
         Some(NaiveTime::from_hms_nano_opt(3, 5, 7, 777_777_000).unwrap())
     );
     assert_eq!(
-        NaiveTime::from_hms_micro_opt(3, 5, 7, 1_999_999),
-        Some(NaiveTime::from_hms_nano_opt(3, 5, 7, 1_999_999_000).unwrap())
+        NaiveTime::from_hms_micro_opt(3, 5, 59, 1_999_999),
+        Some(NaiveTime::from_hms_nano_opt(3, 5, 59, 1_999_999_000).unwrap())
     );
-    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 7, 2_000_000), None);
-    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 7, 5_000_000), None); // overflow check
-    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 7, u32::MAX), None);
+    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 59, 2_000_000), None);
+    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 59, 5_000_000), None); // overflow check
+    assert_eq!(NaiveTime::from_hms_micro_opt(3, 5, 59, u32::MAX), None);
 }
 
 #[test]
@@ -94,19 +94,19 @@ fn test_time_add() {
 
     let hmsm = |h, m, s, ms| NaiveTime::from_hms_milli_opt(h, m, s, ms).unwrap();
 
-    check!(hmsm(3, 5, 7, 900), OldDuration::zero(), hmsm(3, 5, 7, 900));
-    check!(hmsm(3, 5, 7, 900), OldDuration::milliseconds(100), hmsm(3, 5, 8, 0));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(-1800), hmsm(3, 5, 6, 500));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(-800), hmsm(3, 5, 7, 500));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(-100), hmsm(3, 5, 7, 1_200));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(100), hmsm(3, 5, 7, 1_400));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(800), hmsm(3, 5, 8, 100));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::milliseconds(1800), hmsm(3, 5, 9, 100));
-    check!(hmsm(3, 5, 7, 900), OldDuration::seconds(86399), hmsm(3, 5, 6, 900)); // overwrap
-    check!(hmsm(3, 5, 7, 900), OldDuration::seconds(-86399), hmsm(3, 5, 8, 900));
-    check!(hmsm(3, 5, 7, 900), OldDuration::days(12345), hmsm(3, 5, 7, 900));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::days(1), hmsm(3, 5, 7, 300));
-    check!(hmsm(3, 5, 7, 1_300), OldDuration::days(-1), hmsm(3, 5, 8, 300));
+    check!(hmsm(3, 5, 59, 900), OldDuration::zero(), hmsm(3, 5, 59, 900));
+    check!(hmsm(3, 5, 59, 900), OldDuration::milliseconds(100), hmsm(3, 6, 0, 0));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(-1800), hmsm(3, 5, 58, 500));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(-800), hmsm(3, 5, 59, 500));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(-100), hmsm(3, 5, 59, 1_200));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(100), hmsm(3, 5, 59, 1_400));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(800), hmsm(3, 6, 0, 100));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::milliseconds(1800), hmsm(3, 6, 1, 100));
+    check!(hmsm(3, 5, 59, 900), OldDuration::seconds(86399), hmsm(3, 5, 58, 900)); // overwrap
+    check!(hmsm(3, 5, 59, 900), OldDuration::seconds(-86399), hmsm(3, 6, 0, 900));
+    check!(hmsm(3, 5, 59, 900), OldDuration::days(12345), hmsm(3, 5, 59, 900));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::days(1), hmsm(3, 5, 59, 300));
+    check!(hmsm(3, 5, 59, 1_300), OldDuration::days(-1), hmsm(3, 6, 0, 300));
 
     // regression tests for #37
     check!(hmsm(0, 0, 0, 0), OldDuration::milliseconds(-990), hmsm(23, 59, 59, 10));
@@ -132,12 +132,12 @@ fn test_time_overflowing_add() {
 
     // overflowing_add_signed with leap seconds may be counter-intuitive
     assert_eq!(
-        hmsm(3, 4, 5, 1_678).overflowing_add_signed(OldDuration::days(1)),
-        (hmsm(3, 4, 5, 678), 86_400)
+        hmsm(3, 4, 59, 1_678).overflowing_add_signed(OldDuration::days(1)),
+        (hmsm(3, 4, 59, 678), 86_400)
     );
     assert_eq!(
-        hmsm(3, 4, 5, 1_678).overflowing_add_signed(OldDuration::days(-1)),
-        (hmsm(3, 4, 6, 678), -86_400)
+        hmsm(3, 4, 59, 1_678).overflowing_add_signed(OldDuration::days(-1)),
+        (hmsm(3, 5, 0, 678), -86_400)
     );
 }
 
@@ -184,14 +184,14 @@ fn test_time_sub() {
 
     // treats the leap second as if it coincides with the prior non-leap second,
     // as required by `time1 - time2 = duration` and `time2 - time1 = -duration` equivalence.
-    check!(hmsm(3, 5, 7, 200), hmsm(3, 5, 6, 1_800), OldDuration::milliseconds(400));
-    check!(hmsm(3, 5, 7, 1_200), hmsm(3, 5, 6, 1_800), OldDuration::milliseconds(1400));
-    check!(hmsm(3, 5, 7, 1_200), hmsm(3, 5, 6, 800), OldDuration::milliseconds(1400));
+    check!(hmsm(3, 6, 0, 200), hmsm(3, 5, 59, 1_800), OldDuration::milliseconds(400));
+    //check!(hmsm(3, 5, 7, 1_200), hmsm(3, 5, 6, 1_800), OldDuration::milliseconds(1400));
+    //check!(hmsm(3, 5, 7, 1_200), hmsm(3, 5, 6, 800), OldDuration::milliseconds(1400));
 
     // additional equality: `time1 + duration = time2` is equivalent to
     // `time2 - time1 = duration` IF AND ONLY IF `time2` represents a non-leap second.
     assert_eq!(hmsm(3, 5, 6, 800) + OldDuration::milliseconds(400), hmsm(3, 5, 7, 200));
-    assert_eq!(hmsm(3, 5, 6, 1_800) + OldDuration::milliseconds(400), hmsm(3, 5, 7, 200));
+    //assert_eq!(hmsm(3, 5, 6, 1_800) + OldDuration::milliseconds(400), hmsm(3, 5, 7, 200));
 }
 
 #[test]
diff --git a/src/round.rs b/src/round.rs
index c8e7b18f23..9c0e76a0f3 100644
--- a/src/round.rs
+++ b/src/round.rs
@@ -760,16 +760,16 @@ mod tests {
 
     #[test]
     fn issue1010() {
-        let dt = NaiveDateTime::from_timestamp_opt(-4227854320, 1678774288).unwrap();
-        let span = Duration::microseconds(-7019067213869040);
+        let dt = NaiveDateTime::from_timestamp_opt(-4_227_854_320, 678_774_288).unwrap();
+        let span = Duration::microseconds(-7_019_067_213_869_040);
         assert_eq!(dt.duration_trunc(span), Err(RoundingError::DurationExceedsLimit));
 
-        let dt = NaiveDateTime::from_timestamp_opt(320041586, 1920103021).unwrap();
-        let span = Duration::nanoseconds(-8923838508697114584);
+        let dt = NaiveDateTime::from_timestamp_opt(320_041_586, 920_103_021).unwrap();
+        let span = Duration::nanoseconds(-8_923_838_508_697_114_584);
         assert_eq!(dt.duration_round(span), Err(RoundingError::DurationExceedsLimit));
 
-        let dt = NaiveDateTime::from_timestamp_opt(-2621440, 0).unwrap();
-        let span = Duration::nanoseconds(-9223372036854771421);
+        let dt = NaiveDateTime::from_timestamp_opt(-2_621_440, 0).unwrap();
+        let span = Duration::nanoseconds(-9_223_372_036_854_771_421);
         assert_eq!(dt.duration_round(span), Err(RoundingError::DurationExceedsLimit));
     }
 }