One of the great things about MOSS publishing sites is the ability to schedule the start and end dates for content publication. However, if you choose to provision your site collection using the out-of-the-box Collaboration Portal site template instead of the Publishing Portal site template, the scheduling option shown below isn't automatically available when creating new publishing pages within a site. But, all is not lost!
To enable the "Page Settings and Schedule" menu option on a site provisioned using the Collaboration Portal site template, simply enable scheduling of items in the site's Pages document library. To do this using the browser:-
Click Site Actions > View All Site Content. On the All Site Content page, under Document Libraries, click on Pages. On the Pages home page, click Settings > Document Library Settings. On the Customize Pages page under General Settings, click Manage item scheduling. On the Manage Item Scheduling page, check Enable scheduling of items in this list and click OK.