Merge pull request #267 from WiredSharp/feature/timezone_defaulting

use system timezone as default

fish_right_prompt.fish

@@ -63,7 +63,9 @@ function __bobthefish_timestamp -S -d 'Show the current timestamp'
     or set -l theme_date_format "+%c"
 
     echo -n ' '
-    env TZ="$theme_date_timezone" date $theme_date_format
+    set -q theme_date_timezone
+        and env TZ="$theme_date_timezone" date $theme_date_format
+        or date $theme_date_format
 end
 
 function fish_right_prompt -d 'bobthefish is all about the right prompt'