project: Make time format a first-class citizen

The current code deals with 12/24h clock formats almost like
a workaround of the issue. This commit adds proper support to
different clock formats.

src/views/gcal-year-view.c

@@ -97,11 +97,6 @@ struct _GcalYearView
   /* Storage for the accumulated scrolling */
   gdouble               scroll_value;
 
-  /**
-   * clock format from GNOME desktop settings
-   */
-  gboolean            use_24h_format;
-
   /* show week numbers from GNOME Shell settings */
   GSettings          *calendar_settings;
   gboolean            show_week_numbers;
@@ -2108,10 +2103,3 @@ gcal_year_view_set_first_weekday (GcalYearView *year_view,
 {
   year_view->first_weekday = nr_day;
 }
-
-void
-gcal_year_view_set_use_24h_format (GcalYearView *year_view,
-                                   gboolean      use_24h_format)
-{
-  year_view->use_24h_format = use_24h_format;
-}