I have configured No application in the center of notifications. no weather, no stock, no calendar, no calculator. How to return back to the standard application?
Clicking the 'Edit' button at the bottom of the 'Today' panel in Notification Center will show the widgets which have been disabled. Clicking the green plus circle icon beside any of them will re-activate it. When all the widgets you want are active, just click 'Done' button on the bottom-left.
As far as I know the following is a list of the standard widgets supplied with OS X Yosemite
- World Clock