diff --git a/apps/dashboard/src/App.tsx b/apps/dashboard/src/App.tsx
index 4cda49b..6755aa2 100644
--- a/apps/dashboard/src/App.tsx
+++ b/apps/dashboard/src/App.tsx
@@ -16,6 +16,7 @@ import {
 	stepToBrightness,
 } from "./light-control"
 import { StatusSeverity, TubeLine, formatLineName, tflDisruptionsQuery } from "./tfl"
+import { useAutoTheme } from "./use-auto-theme"
 import {
 	DEFAULT_LATITUDE,
 	DEFAULT_LONGITUDE,
@@ -32,6 +33,8 @@ function App() {
 
 	const store = useStore()
 
+	useAutoTheme(DEFAULT_LATITUDE, DEFAULT_LONGITUDE)
+
 	useEffect(() => {
 		const ws = websocket.current
 
diff --git a/apps/dashboard/src/use-auto-theme.ts b/apps/dashboard/src/use-auto-theme.ts
new file mode 100644
index 0000000..ebe660b
--- /dev/null
+++ b/apps/dashboard/src/use-auto-theme.ts
@@ -0,0 +1,110 @@
+import { useEffect } from "react"
+
+interface SunTimes {
+	sunrise: Date
+	sunset: Date
+}
+
+function calculateSunTimes(latitude: number, longitude: number, date: Date = new Date()): SunTimes {
+	const julianDay = getJulianDay(date)
+	const julianCentury = (julianDay - 2451545) / 36525
+
+	const geomMeanLongSun = (280.46646 + julianCentury * (36000.76983 + julianCentury * 0.0003032)) % 360
+	const geomMeanAnomSun = 357.52911 + julianCentury * (35999.05029 - 0.0001537 * julianCentury)
+
+	const eccentEarthOrbit = 0.016708634 - julianCentury * (0.000042037 + 0.0000001267 * julianCentury)
+
+	const sunEqOfCtr =
+		Math.sin(toRadians(geomMeanAnomSun)) * (1.914602 - julianCentury * (0.004817 + 0.000014 * julianCentury)) +
+		Math.sin(toRadians(2 * geomMeanAnomSun)) * (0.019993 - 0.000101 * julianCentury) +
+		Math.sin(toRadians(3 * geomMeanAnomSun)) * 0.000289
+
+	const sunTrueLong = geomMeanLongSun + sunEqOfCtr
+	const sunAppLong = sunTrueLong - 0.00569 - 0.00478 * Math.sin(toRadians(125.04 - 1934.136 * julianCentury))
+
+	const meanObliqEcliptic = 23 + (26 + (21.448 - julianCentury * (46.815 + julianCentury * (0.00059 - julianCentury * 0.001813))) / 60) / 60
+
+	const obliqCorr = meanObliqEcliptic + 0.00256 * Math.cos(toRadians(125.04 - 1934.136 * julianCentury))
+
+	const sunDeclin = toDegrees(Math.asin(Math.sin(toRadians(obliqCorr)) * Math.sin(toRadians(sunAppLong))))
+
+	const varY = Math.tan(toRadians(obliqCorr / 2)) * Math.tan(toRadians(obliqCorr / 2))
+
+	const eqOfTime =
+		4 *
+		toDegrees(
+			varY * Math.sin(2 * toRadians(geomMeanLongSun)) -
+				2 * eccentEarthOrbit * Math.sin(toRadians(geomMeanAnomSun)) +
+				4 * eccentEarthOrbit * varY * Math.sin(toRadians(geomMeanAnomSun)) * Math.cos(2 * toRadians(geomMeanLongSun)) -
+				0.5 * varY * varY * Math.sin(4 * toRadians(geomMeanLongSun)) -
+				1.25 * eccentEarthOrbit * eccentEarthOrbit * Math.sin(2 * toRadians(geomMeanAnomSun)),
+		)
+
+	const haSunrise = toDegrees(Math.acos(Math.cos(toRadians(90.833)) / (Math.cos(toRadians(latitude)) * Math.cos(toRadians(sunDeclin))) - Math.tan(toRadians(latitude)) * Math.tan(toRadians(sunDeclin))))
+
+	const solarNoon = (720 - 4 * longitude - eqOfTime) / 1440
+	const sunriseTime = solarNoon - (haSunrise * 4) / 1440
+	const sunsetTime = solarNoon + (haSunrise * 4) / 1440
+
+	const sunrise = new Date(date)
+	sunrise.setHours(0, 0, 0, 0)
+	sunrise.setMinutes(sunriseTime * 1440)
+
+	const sunset = new Date(date)
+	sunset.setHours(0, 0, 0, 0)
+	sunset.setMinutes(sunsetTime * 1440)
+
+	return { sunrise, sunset }
+}
+
+function getJulianDay(date: Date): number {
+	const year = date.getFullYear()
+	const month = date.getMonth() + 1
+	const day = date.getDate()
+	const hour = date.getHours()
+	const minute = date.getMinutes()
+	const second = date.getSeconds()
+
+	let a = Math.floor((14 - month) / 12)
+	let y = year + 4800 - a
+	let m = month + 12 * a - 3
+
+	let jdn = day + Math.floor((153 * m + 2) / 5) + 365 * y + Math.floor(y / 4) - Math.floor(y / 100) + Math.floor(y / 400) - 32045
+
+	return jdn + (hour - 12) / 24 + minute / 1440 + second / 86400
+}
+
+function toRadians(degrees: number): number {
+	return (degrees * Math.PI) / 180
+}
+
+function toDegrees(radians: number): number {
+	return (radians * 180) / Math.PI
+}
+
+function isDarkMode(latitude: number, longitude: number): boolean {
+	const now = new Date()
+	const { sunrise, sunset } = calculateSunTimes(latitude, longitude, now)
+
+	return now < sunrise || now > sunset
+}
+
+export function useAutoTheme(latitude: number, longitude: number) {
+	useEffect(() => {
+		const updateTheme = () => {
+			const shouldBeDark = isDarkMode(latitude, longitude)
+
+			if (shouldBeDark) {
+				document.documentElement.classList.add("dark")
+			} else {
+				document.documentElement.classList.remove("dark")
+			}
+		}
+
+		updateTheme()
+
+		const interval = setInterval(updateTheme, 60000)
+
+		return () => clearInterval(interval)
+	}, [latitude, longitude])
+}
diff --git a/apps/dashboard/tailwind.config.js b/apps/dashboard/tailwind.config.js
index dca8ba0..6fa4d26 100644
--- a/apps/dashboard/tailwind.config.js
+++ b/apps/dashboard/tailwind.config.js
@@ -1,5 +1,6 @@
 /** @type {import('tailwindcss').Config} */
 export default {
+  darkMode: 'class',
   content: [
     "./index.html",
     "./src/**/*.{js,ts,jsx,tsx}",