A high-precision, modern countdown timer built for iOS.
- Precision Engine: Powered by Combine and
Date-based calculations to ensure zero drift and absolute accuracy. - Reactive UI: The visual progress ring and timer text are perfectly synchronized using reactive streams.
- Modern Glow Zen Design: Reimagined with a deep radial gradient background, vibrant glassmorphism controls, and detailed glow effects.
- Background Support: (Pending)
Most timer apps simply subtract 1 every second (time -= 1). This is naive; if the CPU is busy or the app lags, "1 second" might take 1.05 seconds. Over a 20-minute session, this drift adds up, making the timer inaccurate.
CountdownTimer is different.
It calculates the exact Target End Date (Date + Duration) the moment you press start. On every frame, it recalculates Remaining = Target - Now.
- Zero Drift: Even if the app hangs for 5 seconds, it wakes up with the correct remaining time.
- Self-Correcting: It mathematically guarantees the timer ends exactly when it should.
- Language: Swift 6 (Strict Concurrency Checked)
- Platform: iOS 26.0+
- Architecture: MVVM (Model-View-ViewModel)
- UI Framework: UIKit (Programmatic, No Storyboards)
- Data Flow: Combine
This project demonstrates a professional, scalable architecture for UIKit apps:
- Programmatic UI: Complete removal of Storyboards for cleaner, reviewable, and conflict-free UI code.
- Component-Based: UI is composed of isolated, reusable components (
HeaderView,ControlsView,ProgressBar). - Structured Organization: Clean separation of concerns with dedicated
Models,ViewModels,Components, andResourcesdirectories. - Isolation: Strict adherence to
MainActorisolation and Sendable types where required.
- Clone the repository.
git clone https://github.com/devbyjonni/CountdownTimer.git
- Open
CountdownTimer.xcodeprojin Xcode 16 or later. - Build and run on any iOS 26+ simulator or device.
Copyright © 2026 Jonni Akesson. All rights reserved.