diff --git a/README.md b/README.md
index 6914e85..9add667 100644
--- a/README.md
+++ b/README.md
@@ -72,7 +72,7 @@ User.group_by_week(:created_at, time_zone: "Pacific Time (US & Canada)").count
 # }
 ```
 
-Time zone objects also work.
+Time zone objects also work. In Rails, to see all available time zones, run `$ rake time:zones:all`
 
 ### Week Start
 
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libgit2 0.21.0