feat: add time offset configuration

programs/include/Api/Syscall.hpp

@@ -116,6 +116,10 @@ namespace Montauk {
     // Power management
     static constexpr uint64_t SYS_SUSPEND      = 89;
 
+    // Timezone
+    static constexpr uint64_t SYS_SETTZ         = 90;
+    static constexpr uint64_t SYS_GETTZ         = 91;
+
     // Audio control commands (for SYS_AUDIOCTL)
     static constexpr int AUDIO_CTL_SET_VOLUME = 0;
     static constexpr int AUDIO_CTL_GET_VOLUME = 1;

programs/include/gui/desktop.hpp

@@ -52,6 +52,7 @@ struct DesktopSettings {
     bool show_shadows;      // window shadows on/off
     bool clock_24h;         // 24-hour clock format
     int ui_scale;           // 0=Small, 1=Default, 2=Large
+    int tz_offset_minutes;  // timezone offset from UTC in minutes
 };
 
 struct DesktopState {

programs/include/libc/montauk.h

@@ -94,6 +94,8 @@ extern "C" {
 #define MTK_SYS_AUDIOCLOSE      81
 #define MTK_SYS_AUDIOWRITE      82
 #define MTK_SYS_AUDIOCTL        83
+#define MTK_SYS_SETTZ           90
+#define MTK_SYS_GETTZ           91
 
 #define MTK_SOCK_TCP 1
 #define MTK_SOCK_UDP 2
@@ -411,6 +413,14 @@ static inline void mtk_gettime(mtk_datetime *out) {
     _mtk_syscall1(MTK_SYS_GETTIME, (long)out);
 }
 
+static inline void mtk_settz(int offset_minutes) {
+    _mtk_syscall1(MTK_SYS_SETTZ, (long)offset_minutes);
+}
+
+static inline int mtk_gettz(void) {
+    return (int)_mtk_syscall0(MTK_SYS_GETTZ);
+}
+
 /* ====================================================================
    System info
    ==================================================================== */

programs/include/montauk/syscall.h

@@ -249,6 +249,10 @@ namespace montauk {
     // Timekeeping (wall-clock)
     inline void gettime(Montauk::DateTime* out) { syscall1(Montauk::SYS_GETTIME, (uint64_t)out); }
 
+    // Timezone offset (total minutes from UTC)
+    inline void settz(int offset_minutes) { syscall1(Montauk::SYS_SETTZ, (uint64_t)(int64_t)offset_minutes); }
+    inline int gettz() { return (int)syscall0(Montauk::SYS_GETTZ); }
+
     // Random number generation
     inline int64_t getrandom(void* buf, uint32_t len) {
         return syscall2(Montauk::SYS_GETRANDOM, (uint64_t)buf, (uint64_t)len);

programs/src/desktop/apps/app_settings.cpp

@@ -301,6 +301,35 @@ static void settings_draw_display(Canvas& c, SettingsState* st) {
     draw_toggle_btn(c, bx, y, sbw, btn_h, "Small", s.ui_scale == 0, accent);
     draw_toggle_btn(c, bx + sbw + 8, y, sbw, btn_h, "Default", s.ui_scale == 1, accent);
     draw_toggle_btn(c, bx + (sbw + 8) * 2, y, sbw, btn_h, "Large", s.ui_scale == 2, accent);
+    y += btn_h + 20;
+
+    // Separator
+    c.hline(x, y, c.w - 2 * x, colors::BORDER);
+    y += 16;
+
+    // UTC Offset
+    c.text(x, y + 6, "UTC Offset", colors::TEXT_COLOR);
+    bx = x + 180;
+
+    // [-] button
+    draw_toggle_btn(c, bx, y, 36, btn_h, "-", false, accent);
+
+    // Offset label
+    int off = s.tz_offset_minutes;
+    int offH = off / 60;
+    int offM = off % 60;
+    if (offM < 0) offM = -offM;
+    char tz_label[16];
+    if (offM)
+        snprintf(tz_label, sizeof(tz_label), "UTC%s%d:%02d", offH >= 0 ? "+" : "", offH, offM);
+    else
+        snprintf(tz_label, sizeof(tz_label), "UTC%s%d", offH >= 0 ? "+" : "", offH);
+    int tw = text_width(tz_label);
+    int label_w = 90;
+    c.text(bx + 36 + (label_w - tw) / 2, y + 6, tz_label, colors::TEXT_COLOR);
+
+    // [+] button
+    draw_toggle_btn(c, bx + 36 + label_w, y, 36, btn_h, "+", false, accent);
 }
 
 static void settings_draw_about(Canvas& c, SettingsState* st) {
@@ -392,6 +421,14 @@ static void settings_persist(SettingsState* st) {
     doc.destroy();
 }
 
+static void settings_persist_tz(SettingsState* st) {
+    montauk::toml::Doc doc;
+    doc.init();
+    montauk::config::set_int(&doc, "timezone.offset_minutes", st->desktop->settings.tz_offset_minutes);
+    montauk::config::save("timezone", &doc);
+    doc.destroy();
+}
+
 // ============================================================================
 // Users tab
 // ============================================================================
@@ -1295,6 +1332,27 @@ static void settings_on_mouse(Window* win, MouseEvent& ev) {
             settings_persist(st);
             return;
         }
+        y += btn_h + 20 + 16;
+
+        // UTC Offset: [-] button
+        if (mx >= bx && mx < bx + 36 && cy >= y && cy < y + btn_h) {
+            if (s.tz_offset_minutes > -720) {
+                s.tz_offset_minutes -= 60;
+                montauk::settz(s.tz_offset_minutes);
+                settings_persist_tz(st);
+            }
+            return;
+        }
+        // UTC Offset: [+] button
+        int label_w = 90;
+        if (mx >= bx + 36 + label_w && mx < bx + 36 + label_w + 36 && cy >= y && cy < y + btn_h) {
+            if (s.tz_offset_minutes < 840) {
+                s.tz_offset_minutes += 60;
+                montauk::settz(s.tz_offset_minutes);
+                settings_persist_tz(st);
+            }
+            return;
+        }
     } else if (st->active_tab == 2) {
         // Users tab
         if (!st->desktop->is_admin) return;

programs/src/desktop/main.cpp

@@ -256,6 +256,7 @@ void gui::desktop_init(DesktopState* ds) {
     ds->settings.show_shadows = true;
     ds->settings.clock_24h = true;
     ds->settings.ui_scale = 1;
+    ds->settings.tz_offset_minutes = 60; // default CET (UTC+1)
 
     // Load per-user desktop settings
     {
@@ -311,6 +312,15 @@ void gui::desktop_init(DesktopState* ds) {
 
         doc.destroy();
     }
+
+    // Load timezone config
+    {
+        auto tz = montauk::config::load("timezone");
+        ds->settings.tz_offset_minutes = (int)tz.get_int("timezone.offset_minutes", 60);
+        tz.destroy();
+    }
+    montauk::settz(ds->settings.tz_offset_minutes);
+
     montauk::win_setscale(ds->settings.ui_scale);
 
     ds->ctx_menu_open = false;