Zman

A minimalistic macOS utility that colors the Calendar app with an overlay indicator when your Calendar app timezone differs from your remote team's timezone.

Features

• Detects timezone differences between Calendar.app's viewing timezone and your team's timezone
• Provides a visual overlay on the macOS Calendar app when timezones differ

Requirements

• macOS 26 or later
• Xcode 26.2 or later (to build from source)

Installation

Homebrew (recommended)

brew install plavrenko/zman/zman

After installation, remove the quarantine attribute (the app is not notarized):

xattr -cr "$(brew --prefix)/Caskroom/zman/*/Zman-claude.app"

Build from source

git clone https://github.com/plavrenko/zman.git
cd zman
make build
open build/Release/Zman-claude.app

Or open Zman-claude.xcodeproj in Xcode and press Cmd+R.

How It Works

Zman reads Calendar.app's current viewing timezone setting (the timezone you've set for viewing your calendar) and compares it with your configured team timezone. When these differ, it displays an orange overlay on Calendar.app to remind you that you're viewing your calendar in a different timezone than your team operates in.

Configuration

The app allows you to:

• Set your team's timezone

Privacy

Zman only reads Calendar.app's timezone preferences from your system. It does not access your calendar events or any personal data. No data is sent to external servers or stored outside of your Mac.

Architecture

See ARCHITECTURE.md for diagrams — C4 context/component, data flow, and event/state flow.

Development

Built with:

• SwiftUI
• AppKit (overlay windows, workspace monitoring)
• CoreGraphics (CGWindowList API for window tracking)
• UserDefaults (reading Calendar.app preferences)

Author

Pavel Lavrenko

• Email: pavel@lavrenko.info

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Copyright © 2026 Pavel Lavrenko

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.