diff --git a/fish_right_prompt.fish b/fish_right_prompt.fish
index bd6ee94..04c20ee 100644
--- a/fish_right_prompt.fish
+++ b/fish_right_prompt.fish
@@ -63,7 +63,8 @@ function __bobthefish_timestamp -S -d 'Show the current timestamp'
     or set -l theme_date_format "+%c"
 
     echo -n ' '
-    env TZ="$theme_date_timezone" date $theme_date_format
+    set -q theme_date_timezone; and set ENV_TZ "TZ=$theme_date_timezone"
+    env $ENV_TZ date $theme_date_format
 end
 
 function fish_right_prompt -d 'bobthefish is all about the right prompt'