diff --git a/src/libraries/System.Private.CoreLib/src/System/DateTime.cs b/src/libraries/System.Private.CoreLib/src/System/DateTime.cs
index 778992bc160c5a..9adeb52e4fa481 100644
--- a/src/libraries/System.Private.CoreLib/src/System/DateTime.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/DateTime.cs
@@ -261,8 +261,21 @@ public DateTime(int year, int month, int day, Calendar calendar)
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
         public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar!!, DateTimeKind kind)
-            : this(year, month, day, hour, minute, second, millisecond, 0, calendar, kind)
         {
+            if ((uint)millisecond >= MillisPerSecond) ThrowMillisecondOutOfRange();
+            if ((uint)kind > (uint)DateTimeKind.Local) ThrowInvalidKind();
+
+            if (second != 60 || !s_systemSupportsLeapSeconds)
+            {
+                ulong ticks = calendar.ToDateTime(year, month, day, hour, minute, second, millisecond).UTicks;
+                _dateData = ticks | ((ulong)kind << KindShift);
+            }
+            else
+            {
+                // if we have a leap second, then we adjust it to 59 so that DateTime will consider it the last in the specified minute.
+                this = new DateTime(year, month, day, hour, minute, 59, millisecond, calendar, kind);
+                ValidateLeapSecond();
+            }
         }
 
         // Constructs a DateTime from a given year, month, day, hour,
@@ -364,10 +377,8 @@ public DateTime(int year, int month, int day, int hour, int minute, int second,
         /// For applications in which portability of date and time data or a limited degree of time zone awareness is important,
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
-        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond)
-        {
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond) =>
             _dateData = Init(year, month, day, hour, minute, second, millisecond);
-        }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="DateTime"/> structure to the specified year, month, day, hour, minute, second,
@@ -422,10 +433,8 @@ public DateTime(int year, int month, int day, int hour, int minute, int second,
         /// For applications in which portability of date and time data or a limited degree of time zone awareness is important,
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
-        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, DateTimeKind kind)
-        {
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, DateTimeKind kind) =>
             _dateData = Init(year, month, day, hour, minute, second, millisecond, kind);
-        }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="DateTime"/> structure to the specified year, month, day, hour, minute, second,
@@ -478,8 +487,17 @@ public DateTime(int year, int month, int day, int hour, int minute, int second,
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
         public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar!!)
-            : this(year, month, day, hour, minute, second, millisecond, 0, calendar)
         {
+            if (second != 60 || !s_systemSupportsLeapSeconds)
+            {
+                _dateData = calendar.ToDateTime(year, month, day, hour, minute, second, millisecond).UTicks;
+            }
+            else
+            {
+                // if we have a leap second, then we adjust it to 59 so that DateTime will consider it the last in the specified minute.
+                this = new DateTime(year, month, day, hour, minute, 59, millisecond, calendar);
+                ValidateLeapSecond();
+            }
         }
 
         /// <summary>
@@ -665,13 +683,8 @@ public DateTime(int year, int month, int day, int hour, int minute, int second,
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
         public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond, Calendar calendar!!)
-        : this(year, month, day, hour, minute, second, millisecond, microsecond, calendar, DateTimeKind.Unspecified)
+            : this(year, month, day, hour, minute, second, millisecond, microsecond, calendar, DateTimeKind.Unspecified)
         {
-            if (microsecond is < 0 or >= MicrosecondsPerMillisecond)
-            {
-                ThrowMicrosecondOutOfRange();
-            }
-            _dateData = new DateTime(_dateData).AddMicroseconds(microsecond)._dateData;
         }
 
         /// <summary>
@@ -737,24 +750,13 @@ public DateTime(int year, int month, int day, int hour, int minute, int second,
         /// you can use the corresponding <see cref="DateTimeOffset"/> constructor.
         /// </remarks>
         public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond, Calendar calendar!!, DateTimeKind kind)
+            : this(year, month, day, hour, minute, second, millisecond, calendar, kind)
         {
-            if (second != 60 || !s_systemSupportsLeapSeconds)
-            {
-                if (microsecond is < 0 or >= MicrosecondsPerMillisecond)
-                {
-                    ThrowMicrosecondOutOfRange();
-                }
-
-                var dateTime = calendar.ToDateTime(year, month, day, hour, minute, second, millisecond);
-                dateTime = dateTime.AddMicroseconds(microsecond);
-                _dateData = dateTime.UTicks | ((ulong)kind << KindShift);
-            }
-            else
+            if (microsecond is < 0 or >= MicrosecondsPerMillisecond)
             {
-                // if we have a leap second, then we adjust it to 59 so that DateTime will consider it the last in the specified minute.
-                this = new DateTime(year, month, day, hour, minute, 59, millisecond, microsecond, calendar);
-                ValidateLeapSecond();
+                ThrowMicrosecondOutOfRange();
             }
+            _dateData = new DateTime(_dateData).AddMicroseconds(microsecond)._dateData;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
diff --git a/src/libraries/System.Private.CoreLib/src/System/DateTimeOffset.cs b/src/libraries/System.Private.CoreLib/src/System/DateTimeOffset.cs
index c53aa17621051e..a3f6843d8ec21f 100644
--- a/src/libraries/System.Private.CoreLib/src/System/DateTimeOffset.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/DateTimeOffset.cs
@@ -241,11 +241,11 @@ public DateTimeOffset(int year, int month, int day, int hour, int minute, int se
         /// <paramref name="microsecond"/> is less than 0 or greater than 900.
         /// </exception>
         public DateTimeOffset(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond, TimeSpan offset)
-        : this(year, month, day, hour, minute, second, millisecond, offset)
+            : this(year, month, day, hour, minute, second, millisecond, offset)
         {
             if ((uint)microsecond >= DateTime.MicrosecondsPerMillisecond)
             {
-                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+                throw new ArgumentOutOfRangeException(nameof(microsecond), SR.ArgumentOutOfRange_BadHourMinuteSecond);
             }
             _dateTime = _dateTime.AddMicroseconds(microsecond);
         }
@@ -322,7 +322,7 @@ public DateTimeOffset(int year, int month, int day, int hour, int minute, int se
         {
             if ((uint)microsecond >= DateTime.MicrosecondsPerMillisecond)
             {
-                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+                throw new ArgumentOutOfRangeException(nameof(microsecond), SR.ArgumentOutOfRange_BadHourMinuteSecond);
             }
             _dateTime = _dateTime.AddMicroseconds(microsecond);
         }
diff --git a/src/libraries/System.Runtime/tests/System/DateTimeOffsetTests.cs b/src/libraries/System.Runtime/tests/System/DateTimeOffsetTests.cs
index ae0c345936f058..c5b3a0a719be43 100644
--- a/src/libraries/System.Runtime/tests/System/DateTimeOffsetTests.cs
+++ b/src/libraries/System.Runtime/tests/System/DateTimeOffsetTests.cs
@@ -14,7 +14,7 @@ public static class DateTimeOffsetTests
         [Fact]
         public static void MaxValue()
         {
-            VerifyDateTimeOffset(DateTimeOffset.MaxValue, 9999, 12, 31, 23, 59, 59, 999, 999, TimeSpan.Zero);
+            VerifyDateTimeOffset(DateTimeOffset.MaxValue, 9999, 12, 31, 23, 59, 59, 999, 999, TimeSpan.Zero, 900);
         }
 
         [Fact]
@@ -36,7 +36,7 @@ public static void Ctor_DateTime()
             var dateTimeOffset = new DateTimeOffset(new DateTime(2012, 6, 11, 0, 0, 0, 0, DateTimeKind.Utc));
             VerifyDateTimeOffset(dateTimeOffset, 2012, 6, 11, 0, 0, 0, 0, 0, TimeSpan.Zero);
 
-            dateTimeOffset = new DateTimeOffset(new DateTime(1986, 8, 15, 10, 20, 5, 4, DateTimeKind.Local));
+            dateTimeOffset = new DateTimeOffset(new DateTime(1986, 8, 15, 10, 20, 5, 4, 3, DateTimeKind.Local));
             VerifyDateTimeOffset(dateTimeOffset, 1986, 8, 15, 10, 20, 5, 4, 3, null);
 
             DateTimeOffset today = new DateTimeOffset(DateTime.Today);
@@ -81,7 +81,7 @@ public static void Ctor_DateTime_TimeSpan()
             VerifyDateTimeOffset(dateTimeOffset, 1, 1, 1, 0, 0, 0, 0, 0, TimeSpan.FromHours(-14));
 
             dateTimeOffset = new DateTimeOffset(DateTime.MaxValue, TimeSpan.FromHours(14));
-            VerifyDateTimeOffset(dateTimeOffset, 9999, 12, 31, 23, 59, 59, 999, 999, TimeSpan.FromHours(14));
+            VerifyDateTimeOffset(dateTimeOffset, 9999, 12, 31, 23, 59, 59, 999, 999, TimeSpan.FromHours(14), 900);
 
             dateTimeOffset = new DateTimeOffset(new DateTime(2012, 12, 31, 13, 50, 10), TimeSpan.Zero);
             VerifyDateTimeOffset(dateTimeOffset, 2012, 12, 31, 13, 50, 10, 0, 0, TimeSpan.Zero);
@@ -1138,7 +1138,7 @@ public static void Parse_InvalidDateTimeStyle_ThrowsArgumentException(DateTimeSt
             Assert.Equal(default(DateTimeOffset), dateTimeOffset);
         }
 
-        private static void VerifyDateTimeOffset(DateTimeOffset dateTimeOffset, int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond, TimeSpan? offset)
+        private static void VerifyDateTimeOffset(DateTimeOffset dateTimeOffset, int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond, TimeSpan? offset, int nanosecond = 0)
         {
             Assert.Equal(year, dateTimeOffset.Year);
             Assert.Equal(month, dateTimeOffset.Month);
@@ -1148,7 +1148,7 @@ private static void VerifyDateTimeOffset(DateTimeOffset dateTimeOffset, int year
             Assert.Equal(second, dateTimeOffset.Second);
             Assert.Equal(millisecond, dateTimeOffset.Millisecond);
             Assert.Equal(microsecond, dateTimeOffset.Microsecond);
-            Assert.Equal(0, dateTimeOffset.Nanosecond);
+            Assert.Equal(nanosecond, dateTimeOffset.Nanosecond);
 
             if (offset.HasValue)
             {