My plugin never showed stored value of expiry date. With testing, I was never sure if expiry really happened.
First: I realised the post really expired AFTER the nominated date, not ON it. And it did work, I just still couldn't read back the date I set.
Second, I patched the plugin as follows:
File lib/metabox.php line 46:
<input type="text" id="expirydate" name="expirydate" value="<?php echo get_post_meta($post->ID,"_es_expirydate",true); ?>" readonly="readonly" size="11" /> @23:59
Note 2 changes:
A. The @23:59 reminds me the date was last date of showing, not first date of not showing.
B. (more important) Note the added word "echo" which now displays my set dates correctly on the metabox field.
Now, if only there were a way to CLEAR the expiry date to blank.