diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 82c5dab..c371176 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -19,26 +19,29 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ macOS-latest, ubuntu-latest, windows-latest ]
-    name: ${{ matrix.runs-on }}
-    runs-on: ${{ matrix.runs-on }}
+        os: [ macOS-latest, ubuntu-latest, windows-latest ]
+    name: ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
-      - name: Setup .NET Core
+      - name: Setup .NET
         uses: actions/setup-dotnet@v4.0.0
         with:
-          dotnet-version: 7.0.x
+          dotnet-version: |
+            5.0.x
+            6.0.x
+            7.0.x
 
       - run: dotnet --info
 
-      - if: contains(matrix.runs-on, 'macOS') || contains(matrix.runs-on, 'ubuntu')
+      - if: contains(matrix.os, 'macOS') || contains(matrix.os, 'ubuntu')
         run: ./build.sh
-      - if: matrix.runs-on == 'windows-latest' && !contains(github.ref, 'refs/tags/')
+      - if: matrix.os == 'windows-latest' && !contains(github.ref, 'refs/tags/')
         run: ./build.ps1
-      - if: matrix.runs-on == 'windows-latest' && github.event_name == 'release' && github.event.action == 'published'
+      - if: matrix.os == 'windows-latest' && github.event_name == 'release' && github.event.action == 'published'
         run: |
           ./build.ps1
           dotnet nuget push .\artifacts\*.nupkg -s https://api.nuget.org/v3/index.json -k ${{ secrets.NUGET_API_KEY }}
\ No newline at end of file
diff --git a/src/Serilog.Sinks.Grafana.Loki/Utils/DateTimeOffsetExtensions.cs b/src/Serilog.Sinks.Grafana.Loki/Utils/DateTimeOffsetExtensions.cs
index 0be5c6d..96c353c 100644
--- a/src/Serilog.Sinks.Grafana.Loki/Utils/DateTimeOffsetExtensions.cs
+++ b/src/Serilog.Sinks.Grafana.Loki/Utils/DateTimeOffsetExtensions.cs
@@ -12,14 +12,9 @@ namespace Serilog.Sinks.Grafana.Loki.Utils;
 
 internal static class DateTimeOffsetExtensions
 {
-    #if NET7_0_OR_GREATER
-    internal static string ToUnixNanosecondsString(this DateTimeOffset offset) =>
-        ((offset.ToUnixTimeMilliseconds() * 1000000) +
-         (offset.Microsecond * 1000) +
-         offset.Nanosecond).ToString();
-    #else
-    internal static string ToUnixNanosecondsString(this DateTimeOffset offset) =>
-        (offset.ToUnixTimeMilliseconds() * 1000000).ToString();
-    #endif
+    private const long NanosecondsPerTick = 100;
+    private static readonly DateTimeOffset UnixEpoch = new(1970, 1, 1, 0, 0, 0, TimeSpan.Zero);
 
+    internal static string ToUnixNanosecondsString(this DateTimeOffset offset) =>
+        ((offset - UnixEpoch).Ticks * NanosecondsPerTick).ToString();
 }
\ No newline at end of file
diff --git a/test/Serilog.Sinks.Grafana.Loki.Tests/Serilog.Sinks.Grafana.Loki.Tests.csproj b/test/Serilog.Sinks.Grafana.Loki.Tests/Serilog.Sinks.Grafana.Loki.Tests.csproj
index d87c975..6d0a7a0 100644
--- a/test/Serilog.Sinks.Grafana.Loki.Tests/Serilog.Sinks.Grafana.Loki.Tests.csproj
+++ b/test/Serilog.Sinks.Grafana.Loki.Tests/Serilog.Sinks.Grafana.Loki.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net7.0</TargetFramework>
+        <TargetFrameworks>net5.0;net6.0;net7.0</TargetFrameworks>
         <IsPackable>false</IsPackable>
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
diff --git a/test/Serilog.Sinks.Grafana.Loki.Tests/UtilsTests/DateTimeOffsetExtensionsTests.cs b/test/Serilog.Sinks.Grafana.Loki.Tests/UtilsTests/DateTimeOffsetExtensionsTests.cs
index e7cd1a8..a0f6a2d 100644
--- a/test/Serilog.Sinks.Grafana.Loki.Tests/UtilsTests/DateTimeOffsetExtensionsTests.cs
+++ b/test/Serilog.Sinks.Grafana.Loki.Tests/UtilsTests/DateTimeOffsetExtensionsTests.cs
@@ -6,6 +6,7 @@ namespace Serilog.Sinks.Grafana.Loki.Tests.UtilsTests;
 
 public class DateTimeOffsetExtensionsTests
 {
+    #if NET7_0_OR_GREATER
     [Fact]
     public void UnixEpochShouldBeConvertedCorrectly()
     {
@@ -17,25 +18,39 @@ public void UnixEpochShouldBeConvertedCorrectly()
     }
 
     [Fact]
-    public void DateTimeOffsetShouldBeConvertedCorrectly()
+    public void DateTimeNanosecondsOffsetShouldBeConvertedCorrectly()
     {
-        var dateTimeOffset = new DateTimeOffset(2021, 05, 25, 12, 00, 00, TimeSpan.Zero);
+        var dateTimeOffset = new DateTimeOffset(2021, 05, 25, 12, 00, 00, 777, 888, TimeSpan.Zero).AddMicroseconds(0.999); // There is no other way to set nanoseconds
 
         var result = dateTimeOffset.ToUnixNanosecondsString();
 
-        result.ShouldBe("1621944000000000000");
+        result.ShouldBe("1621944000777888900");
+    }
+
+    #else
+    [Fact]
+    public void UnixEpochShouldBeConvertedCorrectly()
+    {
+        var epoch = new DateTimeOffset(1970, 1, 1, 0, 0, 0, TimeSpan.Zero);
+
+        var result = epoch.ToUnixNanosecondsString();
+
+        result.ShouldBe("0");
     }
 
-#if NET7_0_OR_GREATER
     [Fact]
     public void DateTimeNanosecondsOffsetShouldBeConvertedCorrectly()
     {
-        var dateTimeOffset =
-            new DateTimeOffset(2021, 05, 25, 12, 00, 00, 777, 888, TimeSpan.Zero).AddMicroseconds(0.999); // There is no other way to set nanoseconds
+        const long nanosecondsPerTick = 100;
+
+        var ticks = new DateTimeOffset(2021, 05, 25, 12, 00, 00, TimeSpan.Zero).Ticks;
+        ticks += 777888999 / nanosecondsPerTick;
+
+        var dateTimeOffset = new DateTimeOffset(ticks, TimeSpan.Zero);
 
         var result = dateTimeOffset.ToUnixNanosecondsString();
 
         result.ShouldBe("1621944000777888900");
     }
-#endif
+    #endif
 }
\ No newline at end of file