military time-format?

ATM this is not possible. Perhaps it should be the default 24-hours display format.
This modification will do the trick:

--- office_hours.theme.inc	(revision 1498)
+++ office_hours.theme.inc	(working copy)
@@ -34,7 +34,7 @@
                     'office_hours_time_range',
                     array(
                       'times'       => $block_times,
-                      'format'      => empty($settings['hoursformat']) ? 'G:i' : 'g:i a',
+                      'format'      => empty($settings['hoursformat']) ? 'H:i' : 'g:i a',
                       'separator'   => $settings['separator_hours_hours'],
                     )
                   );

The new option is added with this commit.
There are now 3 options to show a time. So, there is no free-form formatting of the time, yet.