Move time update logic from display module to time manager

components/time/time_manager.h

@@ -27,11 +27,18 @@ typedef enum {
 	WEEK_DAY_SUNDAY,
 } WeekDay;
 
+typedef void (*TimeCallback)(const Time *time);
+
 /**
  * Initialize the time module.
  */
 void time_manager_init(void);
 
+/**
+ * Add a callback to be regularly invoked with time updates.
+ */
+void add_time_callback(TimeCallback callback);
+
 /**
  * Get the current time.
  */