public static String format(final long millis, final String pattern) {
        return format(new Date(millis), pattern, null, null);
    }
public static String format ( final long millis , final String pattern ) { return format ( new Date ( millis ) , pattern , null , null ) ; }
<p>Formats a date/time into a specific pattern.</p>

@param millis  the date to format expressed in milliseconds
@param pattern  the pattern to use to format the date, not null
@return the formatted date