Carefully pull the crown outwards from the case (i.e. do not pull very hard), and when it clicks out you will be able to move the hour and minute hands. Move the hands forward (in time), but not too quickly. When they reach and pass 12:00, the date should change. Of course the date changes every 24 hours, not 12, so if it doesn't change on the first pass, it will on the second. Move the hands past the 12:15 mark, then gently reverse and bring them back (anti-clockwise) to around the 11:45 mark. Then repeat the process and the date should change again.
This function is called a "semi-quickset" date change, allowing the user to conveniently set the correct date after the watch has been idle.
I am guessing based on the caliber that it will work this way, but if, for some reason, it does not have that feature, you can simply rotate the hands forward as many times as necessary (past 12:00) to reach the correct date.
When you are finished, press the crown back in towards the case, and it will return to the default (winding) position. When you plan to use the watch after it has been idle, it is a good idea to gently wind it manually (10 revolutions should suffice) in order to give it some initial power. In other words, even though it is an automatic movement, it can be wound manually, and should be in order to "jump-start" it when it has been idle.
Regards,
Tony C.