Merge pull request #280 from classyk12/fix/DateTime_Kind

fix: DateTime Kind preservation

Author: joaomatossilva

src/DateTimeExtensions/GeneralDateTimeExtensions.cs

@@ -126,7 +126,7 @@ public static DateTime SetTime(this DateTime date, int hour, int minute, int sec
 
         public static DateTime SetTime(this DateTime date, int hour, int minute, int second, int millisecond)
         {
-            return new DateTime(date.Year, date.Month, date.Day, hour, minute, second, millisecond);
+            return new DateTime(date.Year, date.Month, date.Day, hour, minute, second, millisecond, date.Kind);
         }
 
         /// <summary>
@@ -137,7 +137,7 @@ public static DateTime SetTime(this DateTime date, int hour, int minute, int sec
         /// <returns>The new floored DateTime object</returns>
         public static DateTime Floor(this DateTime dt, TimeSpan interval)
         {
-            return dt.AddTicks(-(dt.Ticks%interval.Ticks));
+            return dt.AddTicks(-(dt.Ticks % interval.Ticks));
         }
 
         /// <summary>
@@ -148,7 +148,7 @@ public static DateTime Floor(this DateTime dt, TimeSpan interval)
         /// <returns>The new ceilinged DateTime object</returns>
         public static DateTime Ceiling(this DateTime dt, TimeSpan interval)
         {
-            return dt.AddTicks(interval.Ticks - (dt.Ticks%interval.Ticks));
+            return dt.AddTicks(interval.Ticks - (dt.Ticks % interval.Ticks));
         }
 
         /// <summary>
@@ -160,7 +160,7 @@ public static DateTime Ceiling(this DateTime dt, TimeSpan interval)
         public static DateTime Round(this DateTime dt, TimeSpan interval)
         {
             var halfIntervalTicks = ((interval.Ticks + 1) >> 1);
-            return dt.AddTicks(halfIntervalTicks - ((dt.Ticks + halfIntervalTicks)%interval.Ticks));
+            return dt.AddTicks(halfIntervalTicks - ((dt.Ticks + halfIntervalTicks) % interval.Ticks));
         }
 
         /// <summary>

src/DateTimeExtensions/NaturalText/DateDiff.cs

@@ -59,6 +59,14 @@ public DateDiff(DateTime startDate, DateTime endDate) : this()
                 Days += daysInMonth - startDate.Day + endDate.Day;
             }
 
+            //adjust month difference for february and leap years
+            var daysInMonthForEndDate = DateTime.DaysInMonth(endDate.Year, endDate.Month);
+            if (daysInMonthForEndDate > 27 && daysInMonthForEndDate <= 29 && Days > 27 && Days <= 29)
+            {
+                Months = 0;
+                Days = 0;
+            }
+
             if (Months + endDate.Month >= startDate.Month)
             {
                 Months += endDate.Month - startDate.Month;

tests/DateTimeExtensions.Tests/GeneralDateTimeExtensionsTests.cs

@@ -0,0 +1,105 @@
+using System;
+using NUnit.Framework;
+
+namespace DateTimeExtensions.Tests
+{
+    [TestFixture]
+    public class GeneralDateTimeExtensionsTests
+    { 
+        [Test]
+        public void SetTime_Preserves_Utc_Kind()
+        {
+            // Arrange  
+            DateTime utcDate = new(2026, 7, 7, 14, 0, 0, DateTimeKind.Utc);
+
+            // Act  
+            DateTime result = utcDate.SetTime(15);
+            Assert.Multiple(() =>
+            {
+
+                // Assert  
+                Assert.That(result.Kind, Is.EqualTo(DateTimeKind.Utc));
+                Assert.That(result.Hour, Is.EqualTo(15));
+                Assert.That(result.Minute, Is.EqualTo(0));
+                Assert.That(result.Second, Is.EqualTo(0));
+                Assert.That(result.Millisecond, Is.EqualTo(0));
+            });
+        }
+
+        [Test]
+        public void SetTime_Preserves_Local_Kind()
+        {
+            // Arrange  
+            DateTime localDate = new(2026, 7, 7, 14, 0, 0, DateTimeKind.Local);
+
+            // Act  
+            DateTime result = localDate.SetTime(15, 30);
+            Assert.Multiple(() =>
+            {
+
+                // Assert  
+                Assert.That(result.Kind, Is.EqualTo(DateTimeKind.Local));
+                Assert.That(result.Hour, Is.EqualTo(15));
+                Assert.That(result.Minute, Is.EqualTo(30));
+            });
+        }
+
+        [Test]
+        public void SetTime_Preserves_Unspecified_Kind()
+        {
+            // Arrange  
+            DateTime unspecifiedDate = new(2026, 7, 7, 14, 0, 0, DateTimeKind.Unspecified);
+
+            // Act  
+            DateTime result = unspecifiedDate.SetTime(15, 30, 45);
+            Assert.Multiple(() =>
+            {
+
+                // Assert  
+                Assert.That(result.Kind, Is.EqualTo(DateTimeKind.Unspecified));
+                Assert.That(result.Hour, Is.EqualTo(15));
+                Assert.That(result.Minute, Is.EqualTo(30));
+                Assert.That(result.Second, Is.EqualTo(45));
+            });
+        }
+
+        [Test]
+        public void SetTime_With_Milliseconds_Preserves_Kind()
+        {
+            // Arrange  
+            DateTime utcDate = new(2026, 7, 7, 14, 0, 0, DateTimeKind.Utc);
+
+            // Act  
+            DateTime result = utcDate.SetTime(15, 30, 45, 500);
+            Assert.Multiple(() =>
+            {
+
+                // Assert  
+                Assert.That(result.Kind, Is.EqualTo(DateTimeKind.Utc));
+                Assert.That(result.Hour, Is.EqualTo(15));
+                Assert.That(result.Minute, Is.EqualTo(30));
+                Assert.That(result.Second, Is.EqualTo(45));
+                Assert.That(result.Millisecond, Is.EqualTo(500));
+            });
+        }
+
+        [Test]
+        [TestCase(DateTimeKind.Utc)]
+        [TestCase(DateTimeKind.Local)]
+        [TestCase(DateTimeKind.Unspecified)]
+        public void SetTime_All_Overloads_Preserve_Kind(DateTimeKind kind)
+        {
+            // Arrange  
+            DateTime originalDate = new(2026, 7, 7, 14, 0, 0, kind);
+            Assert.Multiple(() =>
+            {
+
+                // Act & Assert - Test all overloads  
+                Assert.That(originalDate.SetTime(15).Kind, Is.EqualTo(kind));
+                Assert.That(originalDate.SetTime(15, 30).Kind, Is.EqualTo(kind));
+                Assert.That(originalDate.SetTime(15, 30, 45).Kind, Is.EqualTo(kind));
+                Assert.That(originalDate.SetTime(15, 30, 45, 500).Kind, Is.EqualTo(kind));
+            });
+        }
+    }
+}