Charts on the Summary page are defaulted to be intraday.

To change the default, click the "Edit" button located on top of the chart. You can set the Small Chart to default to either 1-day, 5-days, or 1-year.

You'll need to log in with your Yahoo!Xtra ID in order to change the default chart settings. If you don't have a free Yahoo!Xtra ID, just follow the instructions provided when you click the button and you can sign up easily.