diff --git a/Personnummer.Tests/CoordinationNumberTests.cs b/Personnummer.Tests/CoordinationNumberTests.cs
index 929fac1..a76a8f2 100644
--- a/Personnummer.Tests/CoordinationNumberTests.cs
+++ b/Personnummer.Tests/CoordinationNumberTests.cs
@@ -122,13 +122,12 @@ public void TestParseInvalidCn(PersonnummerData ssn)
             }));
         }
 
-#if NET8_0_OR_GREATER
         [Theory]
         [ClassData(typeof(ValidCnDataProvider))]
         public void TestAgeCn(PersonnummerData ssn)
         {
-            var timeProvider = new TestTimeProvider();
-            var localNow = timeProvider.GetLocalNow();
+            var clock = new TestClock();
+            var localNow = clock.GetNow();
 
             int day = int.Parse(ssn.LongFormat.Substring(ssn.LongFormat.Length - 6, 2)) - 60;
             string strDay = day < 10 ? $"0{day}" : day.ToString();
@@ -140,13 +139,12 @@ public void TestAgeCn(PersonnummerData ssn)
                 years--;
             }
 
-            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedLong, new Personnummer.Options { AllowCoordinationNumber = true, TimeProvider = timeProvider }).Age);
-            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedFormat, new Personnummer.Options { AllowCoordinationNumber = true, TimeProvider = timeProvider }).Age);
-            Assert.Equal(years, Personnummer.Parse(ssn.LongFormat, new Personnummer.Options { AllowCoordinationNumber = true, TimeProvider = timeProvider }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedLong, new Personnummer.Options { AllowCoordinationNumber = true, Now = clock.GetNow }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedFormat, new Personnummer.Options { AllowCoordinationNumber = true, Now = clock.GetNow }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.LongFormat, new Personnummer.Options { AllowCoordinationNumber = true, Now = clock.GetNow }).Age);
             // Du to age not being possible to fetch from >100 year short format without separator, we aught to check this here.
-            Assert.Equal(years > 99 ? years - 100 : years, Personnummer.Parse(ssn.ShortFormat, new Personnummer.Options { AllowCoordinationNumber = true, TimeProvider = timeProvider }).Age);
+            Assert.Equal(years > 99 ? years - 100 : years, Personnummer.Parse(ssn.ShortFormat, new Personnummer.Options { AllowCoordinationNumber = true, Now = clock.GetNow }).Age);
         }
-#endif
 
         [Theory]
         [ClassData(typeof(ValidCnDataProvider))]
diff --git a/Personnummer.Tests/PersonnummerTests.cs b/Personnummer.Tests/PersonnummerTests.cs
index 6a4de8e..49801b8 100644
--- a/Personnummer.Tests/PersonnummerTests.cs
+++ b/Personnummer.Tests/PersonnummerTests.cs
@@ -76,13 +76,12 @@ public void TestParseInvalid(PersonnummerData ssn)
         }
 
 
-#if NET8_0_OR_GREATER // Requires TimeProvider.
         [Theory]
         [ClassData(typeof(ValidSsnDataProvider))]
         public void TestAge(PersonnummerData ssn)
         {
-            var timeProvider = new TestTimeProvider();
-            var localNow = timeProvider.GetLocalNow();
+            var clock = new TestClock();
+            var localNow = clock.GetNow();
             DateTime dt = DateTime.ParseExact(ssn.LongFormat.Substring(0, ssn.LongFormat.Length - 4), "yyyyMMdd", CultureInfo.InvariantCulture, DateTimeStyles.None);
 
             var years = localNow.Year - dt.Year;
@@ -91,28 +90,26 @@ public void TestAge(PersonnummerData ssn)
                 years--;
             }
 
-            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedLong, new Personnummer.Options { AllowCoordinationNumber = false, TimeProvider = timeProvider }).Age);
-            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedFormat, new Personnummer.Options { AllowCoordinationNumber = false, TimeProvider = timeProvider }).Age);
-            Assert.Equal(years, Personnummer.Parse(ssn.LongFormat, new Personnummer.Options { AllowCoordinationNumber = false, TimeProvider = timeProvider }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedLong, new Personnummer.Options { AllowCoordinationNumber = false, Now = clock.GetNow }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.SeparatedFormat, new Personnummer.Options { AllowCoordinationNumber = false, Now = clock.GetNow }).Age);
+            Assert.Equal(years, Personnummer.Parse(ssn.LongFormat, new Personnummer.Options { AllowCoordinationNumber = false, Now = clock.GetNow }).Age);
             // Du to age not being possible to fetch from >100 year short format without separator, we aught to check this here.
-            Assert.Equal(years > 99 ? years - 100 : years, Personnummer.Parse(ssn.ShortFormat, new Personnummer.Options { AllowCoordinationNumber = false, TimeProvider = timeProvider }).Age);
+            Assert.Equal(years > 99 ? years - 100 : years, Personnummer.Parse(ssn.ShortFormat, new Personnummer.Options { AllowCoordinationNumber = false, Now = clock.GetNow }).Age);
         }
 
         [Fact]
         public void TestEdgeCasesAroundBirthday()
         {
-            var timeProvider = new TestTimeProvider
+            var clock = new TestClock
             {
                 Now = DateTimeOffset.Parse("2090-01-09 12:00")
             };
 
-            Assert.Equal(10, new Personnummer("20800108-6670", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Had birthday yesterday
-            Assert.Equal(10, new Personnummer("20800109-8287", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Birthday today
-            Assert.Equal(9, new Personnummer("20800110-8516", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Upcoming Birthday tomorrow
+            Assert.Equal(10, new Personnummer("20800108-6670", new Personnummer.Options() {Now = clock.GetNow} ).Age); // Had birthday yesterday
+            Assert.Equal(10, new Personnummer("20800109-8287", new Personnummer.Options() {Now = clock.GetNow} ).Age); // Birthday today
+            Assert.Equal(9, new Personnummer("20800110-8516", new Personnummer.Options() {Now = clock.GetNow} ).Age); // Upcoming Birthday tomorrow
         }
 
-#endif
-
         [Theory]
         [ClassData(typeof(ValidSsnDataProvider))]
         public void TestFormat(PersonnummerData ssn)
diff --git a/Personnummer.Tests/TestClock.cs b/Personnummer.Tests/TestClock.cs
new file mode 100644
index 0000000..f1bcb78
--- /dev/null
+++ b/Personnummer.Tests/TestClock.cs
@@ -0,0 +1,16 @@
+using System;
+
+namespace Personnummer.Tests;
+
+public sealed class TestClock
+{
+    public DateTimeOffset Now { get; set; } = new(
+        new DateTime(2025, 1, 1, 0, 0, 1),
+        TimeSpan.Zero
+    );
+
+    public DateTimeOffset GetNow()
+    {
+        return Now;
+    }
+}
\ No newline at end of file
diff --git a/Personnummer.Tests/TestTimeProvider.cs b/Personnummer.Tests/TestTimeProvider.cs
deleted file mode 100644
index e2b67e3..0000000
--- a/Personnummer.Tests/TestTimeProvider.cs
+++ /dev/null
@@ -1,26 +0,0 @@
-using System;
-
-namespace Personnummer.Tests;
-
-#if NET8_0_OR_GREATER
-
-/// <summary>
-/// TimeProvider which always returns the same date: 2025 01 01 00:00:01 with UTC timezone on local time.
-/// </summary>
-public class TestTimeProvider : TimeProvider
-{
-    internal DateTimeOffset Now { get; set; } = new(
-        new DateOnly(2025, 1, 1),
-        new TimeOnly(0, 0, 0, 1),
-        TimeSpan.Zero
-    );
-
-    public override DateTimeOffset GetUtcNow()
-    {
-        return Now;
-    }
-
-    public override TimeZoneInfo LocalTimeZone { get; } = TimeZoneInfo.Utc;
-}
-
-#endif
diff --git a/Personnummer/Personnummer.cs b/Personnummer/Personnummer.cs
index 4cf7ce9..aea89ab 100644
--- a/Personnummer/Personnummer.cs
+++ b/Personnummer/Personnummer.cs
@@ -13,6 +13,7 @@ public Options()
             {
                 AllowInterimNumber = false;
                 AllowCoordinationNumber = true;
+                Now = () => DateTimeOffset.Now;
             }
 
             /// <summary>
@@ -25,20 +26,12 @@ public Options()
             /// </summary>
             public bool AllowInterimNumber { get; set; } = false;
 
-#if (NET8_0_OR_GREATER)
             /// <summary>
-            /// TimeProvider to use in calculations which are time dependent.<br/>
-            /// Uses `GetLocalNow` method.
-            /// <remarks>
-            /// Defaults to System provider.
-            /// </remarks>
+            /// Function to get the current date and time.
             /// </summary>
-            public TimeProvider TimeProvider { private get; init; } = TimeProvider.System;
+            public Func<DateTimeOffset> Now { get; set; }
 
-            internal DateTimeOffset DateTimeNow => TimeProvider.GetLocalNow();
-#else
-            internal DateTimeOffset DateTimeNow => DateTimeOffset.Now;
-#endif
+            internal DateTimeOffset DateTimeNow => Now();
         }
 
         #region Fields and Properties
diff --git a/Personnummer/Personnummer.csproj b/Personnummer/Personnummer.csproj
index 3043dc5..eedf7db 100644
--- a/Personnummer/Personnummer.csproj
+++ b/Personnummer/Personnummer.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1;net48;net10.0;net8.0;net9.0</TargetFrameworks>
     <Company>Personnummer</Company>
     <Authors>Johannes Tegnér, Personnummer Contributors</Authors>
     <Description>Verify Swedish personal identity numbers.</Description>
@@ -19,6 +18,7 @@
     <PackageIcon>icon.png</PackageIcon>
     <PackageReadmeFile>Readme.md</PackageReadmeFile>
     <IncludeDocumentationProjectOutputGroup>true</IncludeDocumentationProjectOutputGroup>
+    <TargetFramework>netstandard2.1</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>