Modernize project with AI (Codex)

.editorconfig

@@ -0,0 +1,19 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.{cs,csproj,props,targets}]
+indent_size = 4
+indent_style = space
+
+[*.cs]
+csharp_new_line_before_open_brace = all
+csharp_style_namespace_declarations = file_scoped:suggestion
+dotnet_sort_system_directives_first = true
+
+[*.{json,yml,yaml}]
+indent_size = 2

.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+updates:
+  - package-ecosystem: nuget
+    directory: /
+    schedule:
+      interval: weekly
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly

.github/workflows/dotnet.yml

@@ -0,0 +1,61 @@
+name: .NET
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
+jobs:
+  build-and-test:
+    name: Build and test (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v5
+        with:
+          global-json-file: global.json
+
+      - name: Restore
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build --configuration Release --no-restore --verbosity minimal
+
+      - name: Test
+        run: dotnet test --configuration Release --no-build --verbosity minimal
+
+  pack:
+    name: Pack NuGet package
+    needs: build-and-test
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v5
+        with:
+          global-json-file: global.json
+
+      - name: Pack
+        run: ./scripts/nuget-pack.sh
+
+      - name: Upload package artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: nuget-packages-${{ github.sha }}
+          path: |
+            artifacts/nuget/*.nupkg
+            artifacts/nuget/*.snupkg
+          if-no-files-found: error

.gitignore

@@ -6,6 +6,7 @@
 *.user
 *.userosscache
 *.sln.docstates
+.vscode/
 
 # User-specific files (MonoDevelop/Xamarin Studio)
 *.userprefs

CHANGELOG.md

@@ -0,0 +1,52 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.3.1] - 2026-08-29
+
+### Changed
+
+- Consolidated the library and tests into modern SDK-style projects.
+- Updated the test suite to .NET 10 and MSTest.Sdk 4.3.3.
+- Replaced AppVeyor with cross-platform GitHub Actions build and test automation.
+- Replaced the checked-in NuGet executable, batch script, and hand-authored nuspec with SDK-native pack and publish scripts.
+- Added deterministic builds, nullable reference types, current analyzers, XML documentation, Source Link metadata, and NuGet symbol packages.
+- Added documented terminal workflows for locally packing and publishing to NuGet.org with a session-only API key.
+- Refreshed package metadata, documentation, and dependency update automation.
+
+### Fixed
+
+- Made tests involving `DateTime.UtcNow` resilient to clock-boundary timing.
+
+## [1.3.0] - 2022-08-30
+
+### Changed
+
+- Removed obsolete package targets and retained the `netstandard2.0` target to eliminate vulnerable dependencies.
+
+## [1.2.0] - 2020-10-14
+
+### Fixed
+
+- Corrected month and year arithmetic for leap years and variable-length months.
+
+### Changed
+
+- Updated NuGet license metadata to use the Apache-2.0 SPDX expression.
+
+## [1.1.0] - 2019-12-23
+
+### Added
+
+- Added the `netstandard2.0` package target.
+
+## [1.0.0] - 2016-12-28
+
+### Added
+
+- First stable release.

DateMath.sln

@@ -1,27 +1,10 @@
-
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
-VisualStudioVersion = 17.2.32630.192
+VisualStudioVersion = 17.0.31903.59
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{1776B3B6-23B5-47A8-B005-7B6275BEB4D6}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DateMath", "src\DateMath\DateMath.csproj", "{F8F8DCCB-A234-41BA-9678-A6AEF659AC02}"
 EndProject
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{B40AEBDC-0E9D-46FD-B6FF-0049CE78ED0D}"
-	ProjectSection(SolutionItems) = preProject
-		.gitignore = .gitignore
-		appveyor.yml = appveyor.yml
-		DateMath.nuspec = DateMath.nuspec
-		LICENSE.md = LICENSE.md
-		nuget.bat = nuget.bat
-		README.md = README.md
-	EndProjectSection
-EndProject
-Project("{D954291E-2A0B-460D-934E-DC6B0785DB48}") = "Shared", "src\Shared\Shared.shproj", "{20D2E708-D4D3-4CD5-8CAD-3AC7AC5E951B}"
-EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DateMathStandard", "src\DateMathStandard\DateMathStandard.csproj", "{F8F8DCCB-A234-41BA-9678-A6AEF659AC02}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Unit.Core", "src\Test.Unit.Core\Test.Unit.Core.csproj", "{79E67BD1-63CD-429E-94E2-4BA807610599}"
-EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Unit.Framework", "src\Test.Unit.Framework\Test.Unit.Framework.csproj", "{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DateMath.Tests", "test\DateMath.Tests\DateMath.Tests.csproj", "{79E67BD1-63CD-429E-94E2-4BA807610599}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -37,25 +20,11 @@ Global
 		{79E67BD1-63CD-429E-94E2-4BA807610599}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{79E67BD1-63CD-429E-94E2-4BA807610599}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{79E67BD1-63CD-429E-94E2-4BA807610599}.Release|Any CPU.Build.0 = Release|Any CPU
-		{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
-	GlobalSection(NestedProjects) = preSolution
-		{20D2E708-D4D3-4CD5-8CAD-3AC7AC5E951B} = {1776B3B6-23B5-47A8-B005-7B6275BEB4D6}
-		{F8F8DCCB-A234-41BA-9678-A6AEF659AC02} = {1776B3B6-23B5-47A8-B005-7B6275BEB4D6}
-		{79E67BD1-63CD-429E-94E2-4BA807610599} = {1776B3B6-23B5-47A8-B005-7B6275BEB4D6}
-		{AE67BF2F-A5B9-4A28-BB9F-B21A5AF33BBA} = {1776B3B6-23B5-47A8-B005-7B6275BEB4D6}
-	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {094D2933-4AD2-4E54-A660-C3773059E908}
 	EndGlobalSection
-	GlobalSection(SharedMSBuildProjectFiles) = preSolution
-		src\Shared\Shared.projitems*{20d2e708-d4d3-4cd5-8cad-3ac7ac5e951b}*SharedItemsImports = 13
-		src\Shared\Shared.projitems*{f8f8dccb-a234-41ba-9678-a6aef659ac02}*SharedItemsImports = 5
-	EndGlobalSection
 EndGlobal

Directory.Build.props

@@ -0,0 +1,15 @@
+<Project>
+  <PropertyGroup>
+    <AnalysisLevel>latest-recommended</AnalysisLevel>
+    <Deterministic>true</Deterministic>
+    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(CI)' == 'true'">
+    <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
+  </PropertyGroup>
+</Project>