Sundial

A macOS menu bar app that schedules your monitor's brightness, contrast, and Night Shift by time of day — so your screen matches the room as it shifts from morning to night, without you ever touching a slider.

Sundial drives your monitor's hardware brightness and contrast over DDC (via the BetterDisplay CLI), not a software dimming overlay — so it's the real backlight changing, the same as the buttons on the monitor itself. Night Shift warmth is driven through macOS's built-in Night Shift.

What it does

• Time-of-day presets — define presets like Morning, Day, Evening, Night, each with a brightness, contrast, and Night Shift strength.
• Scheduling — assign a preset to a time; Sundial applies it automatically and smoothly interpolates between presets so the change is gradual, not a jarring jump.
• Live control — drag a slider in the menu bar to adjust the current display immediately.
• Wake handling — re-applies the correct preset when your Mac wakes, so the screen is right the moment you return.
• Launch at login — optional; lives quietly in the menu bar (no Dock icon).

Presets and schedule live in config.json under ~/Library/Application Support/Sundial/.

Requirements

• macOS 14 (Sonoma) or later
• BetterDisplay installed (provides the CLI Sundial uses to set hardware brightness/contrast). Hardware brightness and contrast control are free features.
• A monitor that supports DDC/CI (most external displays do)
• For building: xcodegen (brew install xcodegen) and Xcode

Monitor compatibility

I've only tested Sundial on my own monitor — a Gigabyte M27Q. It controls brightness and contrast over DDC/CI (a VESA standard) via the BetterDisplay CLI, so it should work on most external monitors that support DDC, but I can't promise it works on yours.

If it doesn't, the usual suspects are: DDC/CI is switched off in the monitor's on-screen menu (often the default), the monitor doesn't properly honor the standard brightness/contrast controls, or it's connected over HDMI to an Apple Silicon Mac (hit or miss — DisplayPort/USB-C is more reliable). Built-in laptop and most Apple displays don't use DDC at all.

To keep this from being a mystery, Sundial won't let you create presets until it's confirmed it can actually read your monitor: on first launch you enter your BetterDisplay path and display name, hit Connect Monitor, and presets unlock only if that succeeds. If it works on a monitor not listed here, a note or PR is welcome.

Build & install

./build.sh          # build, install to /Applications, and relaunch

build.sh regenerates the Xcode project from project.yml, builds a Release .app, copies it to /Applications, and relaunches it. Other options:

./build.sh -n       # build only, stage into ./build/Sundial.app (no install)
./build.sh -v       # verbose xcodebuild output
./build.sh --help   # usage

Install via ./build.sh (not by running a Debug build from Xcode) so launch-at-login binds the app in /Applications rather than a transient DerivedData path.

Prefer not to build it yourself? Grab the latest Sundial.app from the Releases page, unzip it, and drag it to /Applications.

First run

1. Click the sun icon in the menu bar — Sundial opens to a setup screen.
2. Confirm the BetterDisplay path (default: /Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay) and enter your display name — any partial match of the monitor name shown in BetterDisplay.
3. Hit Connect Monitor. If Sundial can read your monitor over DDC, presets unlock; otherwise the error tells you what to check (see Monitor compatibility).
4. Edit the presets and schedule to taste. Sundial takes over from there. You can revisit the path/name later via the gear icon.

How it works

Setting	Driven by
Brightness	BetterDisplay CLI → DDC VCP 0x10 (real backlight)
Contrast	BetterDisplay CLI → DDC VCP 0x12
Night Shift	macOS Night Shift (CoreBrightness)

The scheduler picks the active preset for the current time and interpolates between presets for smooth transitions. On wake, it forces a full re-apply so the display state always matches the schedule.

Releasing

To cut a release, bump MARKETING_VERSION in project.yml, commit, push, then run:

./release.sh

It reads the version from project.yml, refuses to run on a dirty or unpushed tree, builds a fresh .app, zips it, tags v<version>, and publishes a GitHub release with the zip attached and auto-generated notes.