Only in b: tags
diff -ru a/unlock_indicator.c b/unlock_indicator.c
--- a/unlock_indicator.c	2015-05-22 11:00:01.849040047 +0200
+++ b/unlock_indicator.c	2015-05-22 11:00:45.945473675 +0200
@@ -25,7 +25,7 @@
 #define BUTTON_SPACE (BUTTON_RADIUS + 5)
 #define BUTTON_CENTER (BUTTON_RADIUS + 5)
 #define BUTTON_DIAMETER (2 * BUTTON_SPACE)
-#define TIME_FORMAT "%l:%M %p"
+#define TIME_FORMAT "%H:%M"
 
 /*******************************************************************************
  * Variables defined in i3lock.c.