Yasnippet invoked org-time-stamp function inserts double timestamp

Question

I created a yasnippet template to quickly timestamp a note I'd like to make in org-mode. The body of the yasnippet file reads

$0 
:PROPERTIES:
:CREATED: `(org-insert-time-stamp nil t t)`
:END:

However, the effect is the CREATED property being populated with double inactive timestamps, e.g., :CREATED: [2015-06-16 Tue 10:08][2015-06-16 Tue 10:08]. Why is this behavior occurring, and how do I prevent the redundant timestamp?

References:

• Elisp - Avoid prompt in interactive function
• in org-mode, how to insert timestamp with today's date?

Note: Trying either one of the methods described in the reference links yields the same doubled timestamp result.

Answer 1

This happens because org-insert-time-stamp inserts a time stamp (like the name says), but also returns the time stamp. Yasnippit inserts the return value but you're also left with the one inserted by the function call. A fix is to capture the return value, leaving only the inserted value: (let ((x (org-insert-time-stamp nil t t )))).

Answer 2

Adapted from an answer found in Elisp - Avoid prompt in interactive function, the following body of the yasnippet file works, but I'm sure there's a better solution using (org-insert-time-stamp) or similar. This also doesn't address the peculiar double timestamp behavior described in the original question.

$0
:PROPERTIES:
:CREATED: `(insert (format-time-string "[%Y-%m-%d %a %H:%M]"))`
:END:

NOTE: This solution does oddly leave two spaces between :CREATED: and the inserted timestamp. I'm not sure why.