Countdown Clock is a small Visual Basic .NET Windows Forms program that displays the years, months, days, hours, minutes, and seconds remaining until a user-specified date and time.
Years ago I used a small program called RCT (Retirement Countdown Timer) that displayed a countdown until retirement. RCT depended on the old Visual Basic 5.0 run-time libraries, so I created this Visual Basic .NET replacement. Its appearance is deliberately similar to RCT, but Countdown Clock is general-purpose: the target date, time, and window-title message are configurable.
Countdown Clock reads its target from EndDate.txt. The first line must have this form:
YYYY-MM-DD HH:MM:SS,Message
For example:
2099-01-01 00:00:00,Retirement Begins In ...
The date and time are interpreted as local wall-clock time in the computer's current local time zone. No time-zone field is required in EndDate.txt. The text after the first comma is displayed in the program's title bar; additional commas may appear in that text.
When the file is read, Countdown Clock validates the local date and time and converts it to UTC using the local time-zone rules. A target that falls in a daylight-saving transition gap (an invalid local time) or in a repeated hour (an ambiguous local time) is rejected rather than silently mapped to the wrong instant.
EndDate.txt is loaded from the same directory as the application. The SDK project automatically copies it to build and publish output. When the target instant has been reached, the countdown timer stops.
The project has been modernized from the traditional .NET Framework 4.8 Visual Basic project format to an SDK-style Windows Forms project targeting .NET 10 (net10.0-windows).
The modernization removes the old App.config and My Project/ machinery. Startup is explicit in Program.vb, while application and assembly settings are kept in the compact SDK-style CountdownClock.vbproj.
The startup code deliberately retains the original Microsoft Sans Serif 8.25-point default font and system-aware DPI mode so that the fixed-size form remains visually close to the original application.
.NET 10 is a Long Term Support release. See Microsoft's .NET support policy and Windows Forms migration guidance.
Use Visual Studio 2026 with the .NET desktop development workload and a .NET 10 SDK, or build from a Developer Command Prompt:
dotnet build CountdownClock.sln -c Release
Normal Visual Studio and SDK-generated directories and per-user files such as .vs/, bin/, obj/, *.suo, and *.user are intentionally excluded from version control by .gitignore.
A framework-dependent, single-file Windows x64 build can be produced with:
dotnet publish CountdownClock.vbproj -c Release -r win-x64 --self-contained false -p:PublishSingleFile=true -p:DebugType=None -p:DebugSymbols=false
That build requires the .NET 10 Desktop Runtime on the target computer. To publish a larger self-contained executable that carries its own .NET runtime, use:
dotnet publish CountdownClock.vbproj -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true -p:DebugType=None -p:DebugSymbols=false
EndDate.txt remains a separate editable companion file and is copied into the publish directory automatically.
A prebuilt Windows executable is retained in release/. The executable currently in that directory is the pre-modernization .NET Framework 4.8 build, retained for convenience until the modern .NET 10 source is published on Windows. Its accompanying Countdown Clock.exe.config belongs only to that .NET Framework build.
Once a .NET 10 build is published, replace the legacy files in release/ with the new published executable and its EndDate.txt; a modern .NET build does not use the old .exe.config file. See release/README.md.
The countdown is decomposed sequentially into years, months, days, hours, minutes, and seconds using .NET DateTime calendar operations. This handles variable month lengths and Gregorian leap years.
The target from EndDate.txt is retained as a local civil time for the calendar decomposition, but it is also converted to UTC using TimeZoneInfo. Each timer update obtains DateTime.UtcNow and uses the UTC values to determine whether the target has actually been reached. This avoids relying on implicit local-time conversions while preserving the intended calendar-style display.
The program does not explicitly model leap seconds.
The calculation approach was based on the C# implementation jwg.cs from the date-difference project.
Countdown-Clock/
├── .gitignore
├── Countdown_Clock_screencap.png
├── CountdownClock.Designer.vb
├── CountdownClock.resx
├── CountdownClock.sln
├── CountdownClock.vb
├── CountdownClock.vbproj
├── EndDate.txt
├── LICENSE
├── Program.vb
├── README.md
└── release/
├── Countdown Clock.exe
├── Countdown Clock.exe.config
├── EndDate.txt
└── README.md
A separate GitHub Pages site is not required: GitHub renders the screenshot directly in this README.
Countdown Clock is licensed under the GNU General Public License, version 3 or later. See LICENSE.