Floating date/time can convert to any timezone ID, keeping Value unchanged

Remove fallback to system's local timezone for floating date/time

Author: axunonb

Ical.Net.Tests/CalDateTimeTests.cs

@@ -73,8 +73,8 @@ public static IEnumerable ToTimeZoneTestCases()
             .SetName($"IANA to BCL: {ianaNy} to {bclCst}");
     }
 
-    [Test(Description = "Calling AsUtc should always return the proper UTC time, even if the TzId has changed")]
-    public void TestTzidChanges()
+    [Test(Description = "A certain date/time value applied to different timezones should return the same UTC date/time")]
+    public void SameDateTimeWithDifferentTzIdShouldReturnSameUtc()
     {
         var someTime = DateTimeOffset.Parse("2018-05-21T11:35:00-04:00");
 
@@ -87,7 +87,7 @@ public void TestTzidChanges()
         Assert.That(berlinUtc, Is.Not.EqualTo(firstUtc));
     }
 
-    [Test, TestCaseSource(nameof(DateTimeKindOverrideTestCases))]
+    [Test, TestCaseSource(nameof(DateTimeKindOverrideTestCases)), Description("DateTimeKind of values is always DateTimeKind.Unspecified")]
     public DateTimeKind DateTimeKindOverrideTests(DateTime dateTime, string tzId)
         => new CalDateTime(dateTime, tzId).Value.Kind;
 
@@ -120,9 +120,9 @@ public static IEnumerable DateTimeKindOverrideTestCases()
             .Returns(DateTimeKind.Unspecified)
             .SetName("DateTime with Kind = Local with null tzid returns DateTimeKind.Unspecified");
 
-        yield return new TestCaseData(DateTime.SpecifyKind(localDt, DateTimeKind.Unspecified), null)
+        yield return new TestCaseData(DateTime.SpecifyKind(localDt, DateTimeKind.Local), null)
             .Returns(DateTimeKind.Unspecified)
-            .SetName("DateTime with Kind = Unspecified and null tzid returns DateTimeKind.Unspecified");
+            .SetName("DateTime with Kind = Local and null tzid returns DateTimeKind.Unspecified");
     }
 
     [Test, TestCaseSource(nameof(ToStringTestCases))]

Ical.Net.Tests/RecurrenceTests.cs

@@ -3786,5 +3786,28 @@ private static DateTime SimpleDateTimeToMatch(IDateTime dt, IDateTime toMatch)
         }
         return dt.Value;
     }
-}
 
+    [Test]
+    public void GetOccurrenceShouldExcludeDtEnd()
+    {
+        var ical = """
+                   BEGIN:VCALENDAR
+                   VERSION:2.0
+                   PRODID:-//github.com/ical-org/ical.net//NONSGML ical.net 5.0//EN
+                   BEGIN:VEVENT
+                   UID:123456
+                   DTSTAMP:20240630T000000Z
+                   DTSTART;VALUE=DATE:20241001
+                   DTEND;VALUE=DATE:20241202
+                   SUMMARY:Don't include the end date of this event
+                   END:VEVENT
+                   END:VCALENDAR
+                   """;
+
+        var calendar = Calendar.Load(ical);
+        // Set start date for occurrences to search to the end date of the event
+        var occurrences = calendar.GetOccurrences(new CalDateTime(2024, 12, 2));
+
+        Assert.That(occurrences, Is.Empty);
+    }
+}

Ical.Net/DataTypes/CalDateTime.cs

@@ -17,10 +17,10 @@ namespace Ical.Net.DataTypes;
 /// The iCalendar equivalent of the .NET <see cref="DateTime"/> class.
 /// <remarks>
 /// In addition to the features of the <see cref="DateTime"/> class, the <see cref="CalDateTime"/>
-/// class handles timezones, and integrates seamlessly into the iCalendar framework.
+/// class handles timezones, floating date/times and integrates seamlessly into the iCalendar framework.
 /// <para/>
 /// Any <see cref="Time"/> values are always rounded to the nearest second.
-/// This is because RFC 5545, Section 3.3.5 does not allow for fractional seconds.
+/// This is because RFC 5545, Section 3.3.5, does not allow for fractional seconds.
 /// </remarks>
 /// </summary>
 public sealed class CalDateTime : EncodableDataType, IDateTime
@@ -357,18 +357,10 @@ public override int GetHashCode()
     /// </summary>
     public static implicit operator CalDateTime(DateTime left) => new CalDateTime(left);
 
-    /// <summary>
-    /// Returns a representation of the <see cref="DateTime"/> in UTC.
-    /// </summary>
-    public DateTime AsUtc => ToTimeZone(UtcTzId).Value;
+/// <inheritdoc/>
+    public DateTime AsUtc => DateTime.SpecifyKind(ToTimeZone(UtcTzId).Value, DateTimeKind.Utc);
 
-    /// <summary>
-    /// Gets the date and time value in the ISO calendar as a <see cref="DateTime"/> type with <see cref="DateTimeKind.Unspecified"/>.
-    /// The value has no associated timezone.
-    /// The precision of the time part is up to seconds.
-    /// <para/>
-    /// The value is equivalent to <seealso cref="NodaTime.LocalDateTime"/>.
-    /// </summary>
+    /// <inheritdoc/>
     public DateTime Value
     {
         get
@@ -477,9 +469,10 @@ public DateTime Value
     }
 
     /// <inheritdoc/>
-    /// <remarks>If <see paramref="otherTzId"/> is not a well-known timezone ID, the system's local timezone will be used.</remarks>
     public IDateTime ToTimeZone(string otherTzId)
     {
+        if (IsFloating) return new CalDateTime(_dateOnly, _timeOnly, otherTzId);
+
         var zonedOriginal = DateUtil.ToZonedDateTimeLeniently(Value, TzId);
         var converted = zonedOriginal.WithZone(DateUtil.GetZone(otherTzId));
 

Ical.Net/DataTypes/IDateTime.cs

@@ -12,6 +12,9 @@ public interface IDateTime : IEncodableDataType, IComparable<IDateTime>, IFormat
 {
     /// <summary>
     /// Converts the date/time to UTC (Coordinated Universal Time)
+    /// If <see cref="IsFloating"/>==<see langword="true"/>
+    /// it means that the <see cref="Value"/> is considered as local time for every timezone:
+    /// The returned <see cref="Value"/> is unchanged, but with <see cref="DateTimeKind.Utc"/>.
     /// </summary>
     DateTime AsUtc { get; }
 
@@ -27,10 +30,12 @@ public interface IDateTime : IEncodableDataType, IComparable<IDateTime>, IFormat
     string? TimeZoneName { get; }
 
     /// <summary>
-    /// Gets the underlying DateTime value. This should always
-    /// use DateTimeKind.Utc, regardless of its actual representation.
-    /// Use IsUtc along with the TZID to control how this
-    /// date/time is handled.
+    /// Gets the date and time value in the ISO calendar as a <see cref="DateTime"/> type with <see cref="DateTimeKind.Unspecified"/>.
+    /// The value has no associated timezone.<br/>
+    /// The precision of the time part is up to seconds.
+    /// <para/>
+    /// Use <see cref="IsUtc"/> along with <see cref="TzId"/> and <see cref="IsFloating"/>
+    /// to control how this date/time is handled.
     /// </summary>
     DateTime Value { get; }
 
@@ -114,6 +119,10 @@ public interface IDateTime : IEncodableDataType, IComparable<IDateTime>, IFormat
     /// <summary>
     /// Converts the <see cref="Value"/> to a date/time
     /// within the specified <see paramref="otherTzId"/> timezone.
+    /// <para/>
+    /// If <see cref="IsFloating"/>==<see langword="true"/>
+    /// it means that the <see cref="Value"/> is considered as local time for every timezone:
+    /// The returned <see cref="Value"/> is unchanged and the <see paramref="otherTzId"/> is set as <see cref="TzId"/>.
     /// </summary>
     IDateTime ToTimeZone(string otherTzId);
     IDateTime Add(TimeSpan ts);