Version: unspecified (using KDE 4.6.2)
Changes of format of system date settings doesn't affect widget-clock. Seems like widget-clock always use some hard-coded date format.
Steps to Reproduce:
Try to change date format (as short date, as long date) and apply settings. Even restart of KDE doesn't change how date is displayed by widget-clock.
Date is displayed in some hard-coded format.
widget-clock should use some system-defined date format - long date or short date.
In KDE 4.7 you can use the SystemSettings format for the date of the Digital Clock applet but you need to restart plasma to make it use it.
*** This bug has been marked as a duplicate of bug 274522 ***