Building a macOS Menu Bar App for the Khmer Lunisolar Calendar with SwiftUI

RithyTep — Wed, 28 Jan 2026 04:22:29 +0000

I recently built KhmerCalendarBar, a macOS menu bar app that displays the Cambodian Chhankitek lunisolar calendar. Here's what I learned.

Why

Cambodia uses a lunisolar calendar called Chhankitek alongside the Gregorian calendar. Public holidays like Khmer New Year, Pchum Ben, and Water Festival are determined by this system. I wanted quick access to Khmer dates without opening a browser.

The Stack

SwiftUI with MenuBarExtra (.window style)
Swift Package Manager — zero external dependencies
create-dmg for styled DMG installers

Architecture

The app uses a single CalendarViewModel (@MainActor, ObservableObject) that manages all state. Views are composable SwiftUI components:

KhmerCalendarBarApp
  └─ MenuBarExtra (popover)
       └─ PopoverContentView
            ├─ TodayHeaderView
            ├─ MonthNavigationView
            ├─ CalendarGridView
            ├─ HolidayListView
            ├─ YearOverviewView
            ├─ ClockView
            ├─ SettingsView
            └─ FooterView

The Hard Part: Chhankitek Conversion

The Khmer lunisolar calendar is complex:

Months alternate between 29 and 30 days
Intercalary months (Adhikameas) are added periodically
The Buddhist era year differs from Gregorian by 543
Each year has an animal cycle (like Chinese zodiac but different)
Waxing and waning phases are tracked per day

The conversion engine maps Gregorian dates to Khmer dates including lunar day, month name, era year, and animal cycle.

Live Menu Bar Updates

The menu bar shows Khmer date + time. Two timers handle updates:

Midnight timer — recalculates date at day change
Minute timer — updates time display every 30 seconds

Key Takeaways

MenuBarExtra with .window style gives you a proper popover
@MainActor on the ViewModel prevents threading issues
Timer-based updates need [weak self] to avoid retain cycles
UNUserNotificationCenter requires explicit authorization on macOS
create-dmg makes distribution easy without an Apple Developer account

Try It

Website: https://khmercalendarbar.rithytep.online
GitHub: https://github.com/RithyTep/KhmerCalendarBar
License: MIT

Contributions welcome!

DEV Community: RithyTep