diff --git a/lisp/ol-bbdb.el b/lisp/ol-bbdb.el
index c6e5ab35f..0953aff57 100644
--- a/lisp/ol-bbdb.el
+++ b/lisp/ol-bbdb.el
@@ -362,7 +362,9 @@ This is used by Org to re-create the anniversary hash table."
 
 ;;;###autoload
 (defun org-bbdb-anniversaries ()
-  "Extract anniversaries from BBDB for display in the agenda."
+  "Extract anniversaries from BBDB for display in the agenda.
+When called programmatically, this function expects the `date'
+variable to be globally bound."
   (require 'bbdb)
   (require 'diary-lib)
   (unless (hash-table-p org-bbdb-anniv-hash)