diff --git a/Ical.Net.Tests/AlarmTest.cs b/Ical.Net.Tests/AlarmTest.cs
index 122e8b8e2..ebd851838 100644
--- a/Ical.Net.Tests/AlarmTest.cs
+++ b/Ical.Net.Tests/AlarmTest.cs
@@ -3,11 +3,14 @@
 // Licensed under the MIT license.
 //
 
+#nullable enable
 using Ical.Net.CalendarComponents;
 using Ical.Net.DataTypes;
 using NUnit.Framework;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
+using Ical.Net.Serialization.DataTypes;
 
 namespace Ical.Net.Tests;
 
diff --git a/Ical.Net.Tests/DeserializationTests.cs b/Ical.Net.Tests/DeserializationTests.cs
index 8a326f1f6..47f787c8b 100644
--- a/Ical.Net.Tests/DeserializationTests.cs
+++ b/Ical.Net.Tests/DeserializationTests.cs
@@ -612,4 +612,45 @@ public void CalendarWithMissingProdIdOrVersion_ShouldLeavePropertiesInvalid()
             Assert.That(deserialized, Does.Not.Contain("PRODID:").And.Not.Contains("VERSION:"));
         });
     }
+
+    [Test, Category("DurationSerializer")]
+    [TestCase("PT1H", 0, 0, 1, 0, 0)]
+    [TestCase("PT1H30M", 0, 0, 1, 30, 0)]
+    [TestCase("PT1H30M45S", 0, 0, 1, 30, 45)]
+    [TestCase("P1D", 0, 1, 0, 0, 0)]
+    [TestCase("-P1D", 0, -1, 0, 0, 0)]
+    [TestCase("P1W", 1, 0, 0, 0, 0)]
+    [TestCase("-P1W", -1, 0, 0, 0, 0)]
+    [TestCase("P0W", null, null, null, null, null)]
+    [TestCase("-P0W")]
+    [TestCase("-P1D", 0, -1, 0, 0, 0)]
+    [TestCase("-P1W", -1, 0, 0, 0, 0)]
+    [TestCase("PT0S", 0, 0, 0, 0, 0)]
+    [TestCase("-PT0S", 0, 0, 0, 0, 0)]
+    [TestCase("-PT1H", 0, 0, -1, 0, 0)]
+    [TestCase("-PT1H30M", 0, 0, -1, -30, 0)]
+    [TestCase("-P1D", 0, -1, 0, 0, 0)]
+    [TestCase("PT125H199M199S", 0, 0, 125, 199, 199)]
+    [TestCase("-PT125H199M199S", 0, 0, -125, -199, -199)]
+    [TestCase("-P0DT0H30M0S", 0, 0, 0, -30, 0)]
+    [TestCase("-P1DT1H", 0, -1, -1, 0, 0)]
+    [TestCase("PT1000H", 0, 0, 1000, 0, 0)]
+    [TestCase("-PT1000H", null, null, -1000, null, null)]
+    public void DurationSerializer_ShouldReturn_ExpectedDuration(string text, int? weeks = null, int? days = null, int? hours = null, int? minutes = null, int? seconds = null)
+    {
+        var s = new DurationSerializer();
+        Assert.That((Duration?) s.Deserialize(new StringReader(text)), Is.EqualTo(new Duration(weeks, days, hours, minutes, seconds)));
+    }
+
+    [Test, Category("DurationSerializer")]
+    [TestCase("")]
+    [TestCase("Invalid")]
+    public void Duration_InvalidArguments_ShouldThrow(string text)
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(new DurationSerializer().Deserialize(new StringReader(text)), Is.Null);
+            Assert.That(Duration.Parse(text), Is.Null);
+        });
+    }
 }
diff --git a/Ical.Net.Tests/SerializationTests.cs b/Ical.Net.Tests/SerializationTests.cs
index df5ea7519..9a4f625bc 100644
--- a/Ical.Net.Tests/SerializationTests.cs
+++ b/Ical.Net.Tests/SerializationTests.cs
@@ -7,6 +7,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Globalization;
+using System.IO;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -348,10 +349,6 @@ public void AttendeesSerialized()
         }
     }
 
-    //todo test event:
-    //-GeographicLocation
-    //-Alarm
-
     [Test]
     public void ZeroDuration_Test()
     {
@@ -359,6 +356,13 @@ public void ZeroDuration_Test()
         Assert.That("P0D".Equals(result, StringComparison.Ordinal), Is.True);
     }
 
+    [Test]
+    public void Duration_FromWeeks()
+    {
+        var weeks = Duration.FromWeeks(4).Weeks;
+        Assert.That(weeks, Is.EqualTo(4));
+    }
+
     [Test]
     public void DurationIsStable_Tests()
     {
diff --git a/Ical.Net/DataTypes/Duration.cs b/Ical.Net/DataTypes/Duration.cs
index 4c751ac64..d70bbda7a 100644
--- a/Ical.Net/DataTypes/Duration.cs
+++ b/Ical.Net/DataTypes/Duration.cs
@@ -22,6 +22,12 @@ public struct Duration
     /// <exception cref="ArgumentException">Thrown if not all non-null arguments have the same sign.</exception>
     public Duration(int? weeks = null, int? days = null, int? hours = null, int? minutes = null, int? seconds = null)
     {
+        weeks = NullIfZero(weeks);
+        days = NullIfZero(days);
+        hours = NullIfZero(hours);
+        minutes = NullIfZero(minutes);
+        seconds = NullIfZero(seconds);
+
         var sign = GetSign(weeks) ?? GetSign(days) ?? GetSign(hours) ?? GetSign(minutes) ?? GetSign(seconds) ?? 1;
         if (
             ((GetSign(weeks) ?? sign) != sign)
@@ -119,8 +125,8 @@ public static Duration FromSeconds(int seconds) =>
     /// Parses the specified value according to RFC 5545.
     /// </summary>
     /// <exception cref="System.FormatException">Thrown if the value is not a valid duration.</exception>
-    public static Duration Parse(string value) =>
-        (Duration) new DurationSerializer().Deserialize(new StringReader(value))!; // throws if null
+    public static Duration? Parse(string value) =>
+        (Duration?) new DurationSerializer().Deserialize(new StringReader(value))!;
 
     /// <summary>
     /// Creates an instance that represents the given time span as exact value, that is, time-only.
@@ -200,7 +206,7 @@ internal bool IsEmpty
     /// <summary>
     /// Returns a negated copy of the given instance.
     /// </summary>
-    public static Duration operator-(Duration d) =>
+    public static Duration operator -(Duration d) =>
         new Duration(-d.Weeks, -d.Days, -d.Hours, -d.Minutes, -d.Seconds);
 
     /// <inheritdoc/>
@@ -215,5 +221,5 @@ internal bool IsEmpty
             < 0 => -1
         };
 
-    private static int? NullIfZero(int v) => (v == 0) ? null : v;
+    private static int? NullIfZero(int? v) => (v == 0) ? null : v;
 }
diff --git a/Ical.Net/Serialization/DataTypes/DurationSerializer.cs b/Ical.Net/Serialization/DataTypes/DurationSerializer.cs
index d17800b08..9abd16f59 100644
--- a/Ical.Net/Serialization/DataTypes/DurationSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/DurationSerializer.cs
@@ -58,6 +58,12 @@ private static string SerializeToString(Duration ts)
         new Regex(@"^(?<sign>\+|-)?P(((?<week>\d+)W)|(?<main>((?<day>\d+)D)?(?<time>T((?<hour>\d+)H)?((?<minute>\d+)M)?((?<second>\d+)S)?)?))$",
             RegexOptions.Compiled | RegexOptions.IgnoreCase, RegexDefaults.Timeout);
 
+    /// <summary>
+    /// Deserializes a string into a <see cref="Duration"/> object.
+    /// </summary>
+    /// <param name="tr"></param>
+    /// <returns>A <see cref="Duration"/> for a valid input pattern, or <see langword="null"/> otherwise.</returns>
+    /// <exception cref="FormatException">Cannot create a <see cref="Duration"/> from the input pattern values.</exception>
     public override object? Deserialize(TextReader tr)
     {
         var value = tr.ReadToEnd();
@@ -68,8 +74,10 @@ private static string SerializeToString(Duration ts)
 
             if (!match.Success)
             {
-                // This happens for EXDATE values, which never have a duration,
-                // and also RDATE values, where the optional duration is missing.
+                // This happens for
+                // * EXDATE values, which never have a duration,
+                // * RDATE values, where the optional duration is missing
+                // * TRIGGER values that are invalid
                 return null;
             }
 
@@ -92,7 +100,7 @@ private static string SerializeToString(Duration ts)
                 days = GetGroupInt("day");
                 if (match.Groups["time"].Success)
                 {
-                    hours  = GetGroupInt("hour");
+                    hours = GetGroupInt("hour");
                     minutes = GetGroupInt("minute");
                     seconds = GetGroupInt("second");
                 }
@@ -100,9 +108,9 @@ private static string SerializeToString(Duration ts)
 
             return new Duration(sign * weeks, sign * days, sign * hours, sign * minutes, sign * seconds);
         }
-        catch
+        catch (Exception ex)
         {
-            throw new FormatException();
+            throw new FormatException(ex.Message, ex);
         }
     }
 }