Insert current date and time quickly in a Word document

   Alt+Shift+D   - Current date.

   Alt+Shift+T   - Current time.

Both, the current date and current time are added as Field into the document (see how to highlight fields):

To change the format of any of these fields in a Word document, do the following:

   1.   Right-click on the field and choose Edit Field... in the popup menu:

   2.   In the Field dialog box, select the format you prefer and click OK:

To avoid changes of a current date or/and time in the completed document, you can use Cut + Keep Text Only combination:

   1.  Select pasted Current Date or/and Current Time.

   2.  Do one of the following:

• On the Home tab, in the Clipboard group, click the Cut:
  
• Press Ctrl+X.

   3.  On the Home tab, in the Clipboard group, in the Paste list, choose Keep Text Only:

See also this tip in French: Insérer rapidement la date et l'heure actuelles.