Have DateTimeWidget include the time zone in its type.

src/bin/work.rs

@@ -25,7 +25,7 @@ fn main() {
     // Realtime upload/download rate for a interface
     bar.push(NetworkSpeedWidget::new(&opts.nic, 6));
 
-    let mut dt = DateTimeWidget::tz("%H:%M %Z".to_string(), "Europe/London".to_string());
+    let mut dt = DateTimeWidget::tz("%H:%M %Z".to_string(), chrono_tz::Europe::London);
     dt.set_colors(&vec![
         TimeColor {
             start: NaiveTime::from_hms(0, 0, 0),

src/widgets/datetime.rs

@@ -1,18 +1,16 @@
-use chrono::NaiveTime;
-use chrono_tz::Tz;
+use std::fmt::Display;
+use chrono::{Local, Utc, NaiveTime, offset::TimeZone};
 
 use i3monkit::Block;
 use i3monkit::ColorRGB;
 use i3monkit::{Widget, WidgetUpdate};
 
 /// The widget that shows local time
-pub struct DateTimeWidget {
+pub struct DateTimeWidget<Tz> {
     /// fmt to format the datetime, see
     /// https://docs.rs/chrono/*/chrono/format/strftime/index.html for documentation.
     fmt: String,
-    /// tz string, values from https://docs.rs/chrono-tz/*/chrono_tz/
-    /// None will use local time.
-    tz: Option<String>,
+    tz: Tz,
     colors: Option<Vec<TimeColor>>,
 }
 
@@ -22,19 +20,21 @@ pub struct TimeColor {
     pub color: ColorRGB,
 }
 
-impl DateTimeWidget {
-    // Create a new time widget
+impl DateTimeWidget<Local> {
     pub fn new(fmt: String) -> Self {
-        DateTimeWidget {
-            fmt,
-            tz: None,
-            colors: None,
-        }
+        DateTimeWidget::<Local>::tz(fmt, Local)
     }
-    pub fn tz(fmt: String, tz: String) -> Self {
+}
+
+impl<Tz> DateTimeWidget<Tz>
+where
+    Tz: TimeZone,
+    Tz::Offset: Display,
+{
+    pub fn tz(fmt: String, tz: Tz) -> Self {
         DateTimeWidget {
             fmt,
-            tz: Some(tz),
+            tz,
             colors: None,
         }
     }
@@ -45,19 +45,15 @@ impl DateTimeWidget {
     }
 }
 
-impl Widget for DateTimeWidget {
+impl<Tz> Widget for DateTimeWidget<Tz>
+where
+    Tz: TimeZone,
+    Tz::Offset: Display,
+{
     fn update(&mut self) -> Option<WidgetUpdate> {
-        let (time, time_string) = match &self.tz {
-            Some(tz) => {
-                let tz: Tz = tz.parse().unwrap();
-                let now = chrono::Local::now();
-                let now = now.with_timezone(&tz);
-                (now.time(), now.format(&self.fmt).to_string())
-            }
-            None => {
-                let now = chrono::Local::now();
-                (now.time(), now.format(&self.fmt).to_string())
-            }
+        let (time, time_string) = {
+            let now = Utc::now().with_timezone(&self.tz);
+            (now.time(), now.format(&self.fmt).to_string())
         };
         let color = if let Some(colors) = &self.colors {
             colors
@@ -81,7 +77,7 @@ impl Widget for DateTimeWidget {
             data.color(color);
         }
         Some(WidgetUpdate {
-            refresh_interval: std::time::Duration::new(1, 0),
+            refresh_interval: std::time::Duration::from_secs(1),
             data: Some(data),
         })
     }