Time zone abbreviations are not unique, so they cannot be analyzed. You can ignore it by putting any non-format character as a placeholder:
moment("Mon Oct 14 01:00:00 BST 2013","ddd MMM DD HH:mm:ss ? YYYY")
But you should know that, ignoring it, you will accept the local time zone of the computer on which the code is running. Set the computer to a different time zone and call .format()and you will see what I mean.
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moment.utc("Mon Oct 14 01:00:00 BST 2013","ddd MMM DD HH:mm:ss ? YYYY")