As I'm given to understand, Beretta's date codes apply only to Italian made guns. The above noted web address should give you information on USA made Beretta products.
On Italian guns, the date code has nothing to do with the serial number, and the date code (these days) is a two letter number within a box, generally on the underside of the barrel.
For example, Italian made guns, an AL-391 Parallel Target I have has a serial no. AA38###x, and a date code CA .... made in 2006, a DT-10 Sporter has a serial no AF03### and a date code BN .... made in 2000.
Here is a list of date codes, from 2006 through 2014 .... sorry, but I don't have the information to complete the list to 2018.
2006 CA, 07 CB, 08 CC, 09 CD 2010 CF, 11 CH, 12 CI, 13 CL, 2014 CM