Insert the Date & Time
You can
include the date and time on your Slide Master. By default, the
control will be placed in a text box in the footer at the bottom of
the slide.
Try it:
Insert the Date & Time
Go to the
Insert Ribbon.
Click on
Date & Time.

What Do
You See? You will be prompted to choose from a list of available
formats.
Memo to Self: You can make the
Date and Time update automatically if you wish. The check box option
is in the bottom, left corner.