diff --git a/src/data/org.gnome.shell.extensions.nightthemeswitcher.gschema.xml b/src/data/org.gnome.shell.extensions.nightthemeswitcher.gschema.xml
index 9797c21..19d09b6 100644
--- a/src/data/org.gnome.shell.extensions.nightthemeswitcher.gschema.xml
+++ b/src/data/org.gnome.shell.extensions.nightthemeswitcher.gschema.xml
@@ -72,15 +72,18 @@ SPDX-License-Identifier: GPL-3.0-or-later
 			<default>false</default>
 		</key>
 		<key name="sunrise" type="d">
+			<range min="0" max="24"/>
 			<default>6</default>
 		</key>
 		<key name="sunset" type="d">
+			<range min="0" max="24"/>
 			<default>20</default>
 		</key>
 		<key name="location" type="(dd)">
 			<default>(91,181)</default>
 		</key>
 		<key name="offset" type="d">
+			<range min="0" max="24"/>
 			<default>0.4</default>
 		</key>
 	</schema>
diff --git a/src/modules/Timer.js b/src/modules/Timer.js
index 25ac585..ba8ab1b 100644
--- a/src/modules/Timer.js
+++ b/src/modules/Timer.js
@@ -350,9 +350,11 @@ var Timer = class extends GObject.Object {
         const timeSunrise = solarNoon - haSunrise * 4 / 1440;
         const timeSunset = solarNoon + haSunrise * 4 / 1440;
 
+        const modulo = (n, m) => ((n % m) + m) % m;
+
         const offset = this.#settings.get_double('offset');
-        const sunrise = timeSunrise * 24 + offset;
-        const sunset = timeSunset * 24 - offset;
+        const sunrise = modulo(timeSunrise * 24 + offset, 24);
+        const sunset = modulo(timeSunset * 24 - offset, 24);
 
         this.#settings.set_double('sunrise', sunrise);
         this.#settings.set_double('sunset', sunset);