The default date format in 
WebCam Monitor is MMM-DD-YYYY. You can change the date format from the ‘Edit Webcam’ settings.
To change the date format, click 
File >> Edit WebCam. On the 
Labels tab, click the 
Configure button for 
Date and Time stamp label. Then select the required date format from the ‘Date and Time Format’ dropdown list. Click Ok to save the settings.

Now the selected date format will appear on the webcam preview.