Here you see the publishing date for the current page. You can also change the publishing date for a previously published page. E.g. if having an article that should be displayed on top in the news portlet again.
In order to change this date, click the arrow in the list. Then there will be a calendar where you can select a new date.
Double arrows at the month will change to previous/next year and the single arrows to previous/next month.
Trippel arrows at the time will change to previous/next hour, double arrows to previous/next minute, and the single arrows to previous/next second.v
It is also possible to type the date in the input field.