feat: add setting for first day of the week (#1854)

* feat: add setting for first day of the week

* fix: extract settings indices

* fix: formatting mistake

* fix(ui): add outline rectangle between settings and reorder settings

* fix: don't set firstDayOfWeek automatically to system's locale

quickshell/Modules/Settings/TimeWeatherTab.qml

@@ -9,6 +9,16 @@ import qs.Modules.Settings.Widgets
 Item {
     id: root
 
+    function weekStartQt() {
+        if (SettingsData.firstDayOfWeek >= 7 || SettingsData.firstDayOfWeek < 0) {
+            return Qt.locale().firstDayOfWeek;
+        }
+        return SettingsData.firstDayOfWeek;
+    }
+    function weekStartJs() {
+        return weekStartQt() % 7;
+    }
+
     DankFlickable {
         anchors.fill: parent
         clip: true
@@ -69,6 +79,35 @@ Item {
                 settingKey: "dateFormat"
                 iconName: "calendar_today"
 
+                SettingsDropdownRow {
+                    tab: "time"
+                    tags: ["first", "day", "week"]
+                    settingKey: "firstDayOfWeek"
+                    text: I18n.tr("First Day of Week")
+                    // Days from Sunday to Saturday in the selected language
+                    // 1st of February 2026 is a Sunday, any Sunday works
+                    options: {
+                        return Array(7).fill(0).map(
+                            (_, i) => new Date(Date.UTC(2026, 2, 1 + i, 0, 0, 0)).toLocaleDateString(
+                                I18n.locale(), "dddd"
+                            )
+                        ).map(
+                            d => d[0].toUpperCase() + d.slice(1)
+                        );
+                    }
+                    currentValue: options[root.weekStartJs()]
+                    onValueChanged: value => {
+                        SettingsData.set("firstDayOfWeek", options.indexOf(value));
+                    }
+                }
+
+                Rectangle {
+                    width: parent.width
+                    height: 1
+                    color: Theme.outline
+                    opacity: 0.15
+                }
+
                 SettingsDropdownRow {
                     tab: "time"
                     tags: ["date", "format", "topbar"]