Convert DateTime<Local> to NaiveDateTime

Use of DateTime<Local> can lead to excessive inspection of the system
timezone.

Instead, propagate only a timezone-compensated NaiveDateTime throughout
the widgets.

src/widgets/clock.rs

@@ -2,21 +2,21 @@ use crate::color::Color;
 use crate::draw::{Font, ROBOTO_REGULAR};
 use crate::widget::{DrawContext, DrawReport, KeyState, ModifiersState, WaitContext, Widget};
 
-use chrono::{DateTime, Duration, Local, Timelike};
+use chrono::{Duration, NaiveDateTime, Timelike};
 
 pub struct Clock {
-    cur_time: DateTime<Local>,
+    cur_time: NaiveDateTime,
     clock_cache: Font,
     size: f32,
 }
 
 impl Clock {
-    pub fn new(size: f32) -> Box<Clock> {
+    pub fn new(time: &NaiveDateTime, size: f32) -> Box<Clock> {
         let mut clock_cache = Font::new(&ROBOTO_REGULAR, size);
         clock_cache.add_str_to_cache("0123456789:");
 
         Box::new(Clock {
-            cur_time: Local::now(),
+            cur_time: time.clone(),
             clock_cache: clock_cache,
             size: size,
         })