--- title: ".NET Timezone: review, setup & limitations · Undominated.ai" canonical: https://undominated.ai/skills/github-dotnet-timezone/ description: "Resolves .NET timezone work through the right library first — TimeZoneConverter for cross-platform, NodaTime for recurring schedules and strict DST arithmetic — and ships both Windows and IANA identifiers on every answer, seven copy-paste code patterns, and the pitfall list from DateTimeKind.Unspecified to DST transitions that skip or repeat local times." --- # .NET Timezone: review, setup & limitations · Undominated.ai > Resolves .NET timezone work through the right library first — TimeZoneConverter for cross-platform, NodaTime for recurring schedules and strict DST arithmetic — and ships both Windows and IANA identifiers on every answer, seven copy-paste code patterns, and the pitfall list from DateTimeKind.Unspecified to DST transitions that skip or repeat local times. [← Explore all skills](/skills/) LANGUAGES AND TOOLING / GitHub community # .NET Timezone Resolves .NET timezone work through the right library first — TimeZoneConverter for cross-platform, NodaTime for recurring schedules and strict DST arithmetic — and ships both Windows and IANA identifiers on every answer, seven copy-paste code patterns, and the pitfall list from DateTimeKind.Unspecified to DST transitions that skip or repeat local times. [See setup guidance ↓](#setup)[Original source ↗](https://github.com/github/awesome-copilot/tree/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone) SOURCE REVIEW Reviewed 2026-10-15 Evidence 5 linked sources Publisher GitHub community Licence [MIT ↗](https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/LICENSE) Revision 7cce7cfb4b61 [Read what was—and wasn’t—checked ↓](#review) “.NET timezone handling guidance for C# applications. Use when working with TimeZoneInfo, DateTimeOffset, NodaTime, UTC conversion, daylight saving time, scheduling across timezones, cross-platform Windows/IANA timezone IDs, or when a .NET user needs the timezone for a city, address, region, or country and copy-paste-ready C# code.” [GitHub community · upstream description ↗](https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/SKILL.md) Our analysis follows below. 01 / THE REASONING ## Why this made the selection. - Routes every request through the right library before any code is written — TimeZoneConverter for cross-platform work, NodaTime when recurring schedules or strict DST rules are in play — instead of letting agents reach for TimeZoneInfo on the wrong platform. - The pitfall list is the real failure set: DateTimeKind.Unspecified as a bug risk, storing DateTime.Now in databases, DST transitions that skip or repeat local times, and Windows versus IANA identifier divergence including between Azure environments. - Ships both identifier systems on every answer — the Windows ID for TimeZoneInfo on Windows, the IANA ID for Linux, containers and NodaTime — with a reference index of common mappings and seven ready code patterns from Windows-only to ambiguous DST timestamps. ### A good fit for - Resolving a timezone for a city, address or region into both Windows and IANA identifiers with working C# code - Choosing between TimeZoneInfo, TimeZoneConverter, DateTimeOffset and NodaTime for a given scenario - Designing persistence and API boundaries that store and transfer UTC correctly - Surface ambiguous place-to-timezone mappings for user selection before producing location-specific code. ### Weigh up before choosing - .NET-specific; the discipline transfers to other stacks but the APIs and libraries do not. - The timezone index reference is a curated common-cases list, not a complete tz database; unusual zones fall back to geographic inference with a note. - Ambiguous locations are handled by listing candidates and asking the user to choose — correct, but it means unattended runs can stop on ambiguity. 02 / THE REVIEW RECORD ## What we actually inspected. Source review has boundaries. A clear record is more useful than a “safe” badge. ### Material inspected - skills/dotnet-timezone/SKILL.md - skills/dotnet-timezone/references directory listing - LICENSE (MIT) - vercel-labs/skills@7407f3893ad4dceab546ac002c3ef806e4000c73:README.md - LICENSE ### Our findings - The references directory is verified to contain the two documents the workflow depends on: timezone-index.md for Windows-to-IANA mappings and code-patterns.md for the seven implementation patterns. - The response shape is bounded: a recommended approach in one sentence, the relevant identifiers, a minimal snippet, package guidance, and one pitfall warning — not an essay. - Ambiguity is handled honestly: when a location matches multiple zones, the skill lists the candidates and asks the user to choose rather than guessing. - Location handling requires both Windows and IANA identifiers, asks the user to resolve ambiguous matches, and separates recurring-schedule/DST patterns from API and data-transfer patterns. ### Not established by this review - No C# code was compiled or run against these patterns; the workflow was read, not executed. - The timezone index was verified to exist, not audited entry by entry for correctness. - Not executed: it was not installed or run. The review applies to the material and revision named here. A newer upstream release can change its behavior. 03 / PUT IT TO WORK ## Add a skill to your workflow. [Upstream setup instructions ↗](https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/README.md) DOCUMENTED COMMAND npx skills add github/awesome-copilot/skills/dotnet-timezone --skill dotnet-timezone Copy command ↗ Run in your terminal to choose your AI tools, project or global scope, and installation method. This short command follows the current upstream version; the review covers the revision shown above. Optional: install the reviewed revision Keeps the original source and installer version where recorded, while leaving your AI tools and installation scope for you to choose. npx skills add https://github.com/github/awesome-copilot/tree/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone --skill dotnet-timezone Copy reviewed-revision command ↗ - Install the complete skill directory; the mapping index and code patterns must travel with the SKILL.md. - Bring the location, identifier or scheduling scenario; the skill answers with identifiers plus a copy-paste snippet. ### Before you start - Node.js/npm for the installer - An agent that supports the Agent Skills format - A .NET codebase or a timezone question about one ### Compatibility Agent Skills-compatible coding agents · C#/.NET applications · Windows, Linux and container deployments where identifier formats diverge ### Reads location or identifier inputs and .NET code; writes C# snippets - Read the provided locations, timezone identifiers or C# code - Write C# snippets and configuration guidance into the response or project - No network access is required by the workflow ### Cost model MIT-licensed instruction package; recommended third-party libraries (TimeZoneConverter, NodaTime) are free and separate. 04 / FOLLOW THE EVIDENCE ## The source trail. Our notes are separate from the original resource. Check upstream before adopting a new version. - [Skill definition at reviewed revision ↗](https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/SKILL.md) Checked 2026-10-07 https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/SKILL.md Supports: summary, upstreamDescription, whySelected, bestFor, limitations, review, access - [Reference directory listing at reviewed revision (timezone index and code patterns) ↗](https://github.com/github/awesome-copilot/tree/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/references) Checked 2026-10-07 https://github.com/github/awesome-copilot/tree/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/references Supports: review, whySelected - [Upstream license (MIT) ↗](https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/LICENSE) Checked 2026-10-07 https://github.com/github/awesome-copilot/blob/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/LICENSE Supports: license - [Skills installer source formats and selective installation ↗](https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/README.md) Checked 2026-10-07 https://github.com/vercel-labs/skills/blob/7407f3893ad4dceab546ac002c3ef806e4000c73/README.md Supports: install - [Pinned continuation review W19 ↗](https://raw.githubusercontent.com/github/awesome-copilot/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/SKILL.md) Checked 2026-10-15 https://raw.githubusercontent.com/github/awesome-copilot/7cce7cfb4b61196c36d7e8eb8475ae84b356b126/skills/dotnet-timezone/SKILL.md Supports: review.findings, bestFor KEEP COMPARING ## Other approaches to consider. Related by category or shared topics. These are alternatives to inspect, not a measured quality order. [### Ruff Recursive Fix ↗ Enforces Python code quality with scoped Ruff runs: safe fixes first, unsafe fixes second with diff review each pass, then targeted manual remediation under explicit stop criteria.](/skills/github-ruff-recursive-fix/)[### Trail of Bits Modern C++ ↗ Pushes new C++ toward C++20, 23, and 26 idioms and a hardened libc++, and stops when the user requires an older standard or the file is C.](/skills/trailofbits-modern-cpp/)[### Turborepo ↗ Monorepo build-system discipline for Turborepo: package tasks instead of root tasks, turbo.json task registration, cache outputs and hashing inputs, environment variables as cache keys, --affected runs, CI setup, and tag-based package boundaries.](/skills/jetbrains-turborepo/) [AI Tools ↗](/tools/)[Skills ↗](/skills/)[Agents ↗](/agents/)[MCP Servers ↗](/mcp-servers/)[Workflows ↗](/workflows/) ## Continue your investigation - [Choose a toolkit](/tools/) - [Inspect execution hosts](/agents/) - [Check tool access](/mcp-servers/) - [Check project dependencies](/check-repo/)