JPKusumi.com presents—

UtcMilliTime

UtcMilliTime is a C# time component (software-defined clock) that yields Unix time milliseconds (Int64) timestamps, similar to JavaScript's Date.now(). It synchronizes with NTP servers and is cross-platform for .NET 8 + .NET 10+, supporting async Main. Mock-friendly via the ITime interface.

On NuGet at: https://www.nuget.org/packages/UtcMilliTime/
On GitHub at: https://github.com/JPKusumi/UtcMilliTime

Versions

• 2.2.3: Patch for NuGet to pick up README.md. Includes all v2.2 features (chaining extensions).
• 2.2.2: Patch for NuGet to pick up README.md. Includes all v2.2 features (chaining extensions).
• 2.2.1: Fixed nullability warnings and improved NuGet README display. Includes all v2.2 features (chaining extensions).
• 2.2.0: Added chaining extensions for Unix timestamps (add/subtract for days, hours, minutes, seconds).
• 2.1.0: Ready for .NET 10; still good for .NET 8+. Accuracy: 1ms (improved precision)
• 2.0.0: First update in six years went cross-platform. Good for .NET 8+.
• 1.0.1: .NET Standard 2.0 (Windows-only, .NET Framework 4.6.1+, .NET Core 2.0+).

Overview

UtcMilliTime provides Int64 timestamps (milliseconds since 1/1/1970 UTC, excluding leap seconds), avoiding the Year 2038 problem with 64-bit integers. It initializes with device time and syncs with NTP servers (default: pool.ntp.org) when permitted, ignoring user-changeable device time thereafter. Supports ISO-8601 string conversion via ToIso8601String.

Note: UtcMilliTime uses a singleton pattern—the clock is shared across the app. All accesses (static or via CreateAsync) refer to the same instance after initialization.

Installation

dotnet add package UtcMilliTime --version 2.2.3

For legacy projects:

dotnet add package UtcMilliTime --version 1.0.1

Usage

By default, the clock initializes with device time and leaves the network alone.

using UtcMilliTime;
  
  ITime time = Clock.Time; // Shorthand for repeated access to the singleton
  time.SuppressNetworkCalls = false; // Enable NTP sync (durable for runtime; execute once)
  var timestamp = time.Now; // Int64 timestamp
  string iso = timestamp.ToIso8601String(); // 2025-07-10T13:00:00.123Z

Important: SuppressNetworkCalls = false grants permission for NTP synchronization. The clock starts with device time; after permission and connectivity, it self-updates to network time. This setting persists for the app's lifetime and must be set explicitly (defaults to true to avoid unintended network use).

With permission, and subject to connectivity, the clock will synchronize itself to network time.

Chaining Extensions for Unix Timestamps

New in v2.2: Fluent methods on long for easy additions and subtractions, ideal for calculating expiration times in JWTs or other auth flows. These operate on Unix seconds (after calling ToUnixTimeSeconds).

using UtcMilliTime;

long nowMilli = Clock.Time.Now;
long iatSeconds = nowMilli.ToUnixTimeSeconds();  // Current time in seconds
long futureSeconds = nowMilli.ToUnixTimeSeconds().AddDays(7).AddHours(1).AddMinutes(30).AddSeconds(45);  // +7 days, 1 hour, 30 min, 45 sec
long pastSeconds = nowMilli.ToUnixTimeSeconds().SubtractDays(30).SubtractHours(12);  // -30 days and 12 hours

NTP Sync Note: By default, SuppressNetworkCalls = true (uses device time only). To enable NTP:

await Clock.CreateAsync();
Clock.Time.SuppressNetworkCalls = false;  // Allows sync if connected

Supporting Async Main

For async initialization in contexts like async Main (returns the shared clock instance):

static async Task Main(string[] args)
{
    var clock = await Clock.CreateAsync();
    clock.SuppressNetworkCalls = false; // Enable sync (triggers SelfUpdateAsync if indicated)
    Console.WriteLine($"Synchronized: {clock.Synchronized}, Time: {clock.Now}, ISO: {clock.Now.ToIso8601String()}");
    // For custom server: await clock.SelfUpdateAsync("custom.ntp.org");
}

Note: CreateAsync initializes and returns the singleton clock (using device time). Synchronization happens only after setting SuppressNetworkCalls = false (via the setter's logic) or manual SelfUpdateAsync calls. This ensures no unintended network traffic.

NetworkTimeAcquired Event

Subscribe to events on the shared instance:

Clock.Time.NetworkTimeAcquired += (sender, e) => Console.WriteLine($"Synced with {e.Server}, Skew: {e.Skew}ms");

Notes

• Silent Failure: SelfUpdateAsync fails silently if connectivity is absent. Check Synchronized for success.
• Leap Seconds: Clock advances during leap seconds, appearing 1 second ahead. Call SelfUpdateAsync() to resync.
• Performance: Use Now for maximum performance; ToIso8601String is slower due to DateTime.

Upgrading from 1.0.1

Version 2.2.3: Public API unchanged (static Clock.Time.Now still works as a singleton).

Migration: Static usage remains the same; for async Main use await Clock.CreateAsync()—it returns the shared clock.

Technical Details

Calculates with Stopwatch.GetTimestamp for high resolution uptime and DateTime.UtcNow for device time. Now is calculated as device_boot_time + GetHighResUptime. The clock is a singleton to ensure consistent time across the app.

Resources and Community

For more information, blog posts, and updates on this and other JP Kusumi creations, visit the JPKusumi.com. Recent blog posts include:

• Key and nonce management best practices.
• Handling cryptographic metadata securely.
• Encrypting JWTs with post-quantum tools.

JPKusumi.com aims to be a resource for developers. There is also a discussion forum, open in the GitHub repo for GreenfieldPQC. Comments and feedback may be directed there.

License

MIT License