Cannot Format Given Object As A Date

When trying to convert the time zone of a date I encountered the log below. java.lang.IllegalArgumentException: Cannot format given Object as a Date..Here is what my code looks like:

1. First I will get the date from the email header by the following code.

String messageDate = (String) mail.headers["Date"];

Output: Wed, 4 Jun 2014 18:30:05 +0800

2. Next I will convert the timezone to EST.

SimpleDateFormat timeZoneConvert = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z");

timeZoneConvert.setTimeZone(TimeZone.getTimeZone(" EST"));

String l_MailDateEST = timeZoneConvert.format(messageDate.trim());

Once the code run I encounter the said error.