How to tune up this little piece of code?

Hi,

I am using Eclipse profiler and have found that the following method,
getDate(), in a utility class was called more than 3000 times and cost 5
seconds of accumulative time.

public class Helper //a utility class
{
    ...//other helping methods

    //get the String and return an object of Date
    public static Date getDate(String str)
    {
        Date aDate = null;
        if (timeString != null)
        {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            format.setTimeZone(TimeZone.getTimeZone("UTC"));
            try
            {
                aDate = format.parse(str);
            }
            catch ... //omitted
        }

        return aDate;
    }
}

I am not very good with code performance. I feel at least something
below should be better:

public class Helper
{
    ...//other helping methods

    private static Date aDate = null;
    private static SimpleDateFormat format = (new
SimpleDateFormat("yyyy-MM-dd
HH:mm:ss")).setTimeZone(TimeZone.getTimeZone("UTC"));
    public static Date getDate(String str) //now the method is much shorter
    {
        if (timeString != null)
        {
            try
            {
                aDate = format.parse(str);
            }
            catch ... //omitted
        }

        return aDate;
    }

}

Do you think my new code is legal? Is better?