First of all, I must say Date Codes are not an absolute way to determine authentcity of Louis Vuitton items. Many Vintage Louis Vuitton do not have Date Codes at all and nowadays almost all fake bags have date codes.
Date code (DC) is also commonly referred to as "serial numbers" and can be used interchangeably. DC were only widely used after the 1990's. The DC was meant for the use of Louis Vuitton employees internally to identify their own handbags. Not for authenticity purposes.
Not all handbags with serial numbers are authentic and not all handbags without a serial number are fake.
Louis Vuitton made in the early 80's had three or four digits only and Louis Vuitton made in the late 80's had three or four digits followed by two letters. I've also seem some vintage handbags with one letter followed by 5 digits.
Date codes since the 90's consists of two letters followed by four numbers.
The first two letters tell you "the country where it is made" and the numbers tell you the "month and year it was manufactured".
For definition of letters, refer to the following: (Be aware that this list is not complete and only Louis Vuitton has the complete list. The following is generated from personal experience) :
France: A1, A2, AA, AO, AC, AN, AR, AS, BA, BJ, CT, DU, ET, FL, FR, MB, MI, NO, ND, RA, RI, SD, SL, SN, SP, SR, TH, VI, VR
USA: FC, FH, FF, LA, OS, SD
Spain: CA, LO, LB, LM, LW
Italy: CE, MA, SA
Serial number "SP0011" means the bag is made in France and it was made on January, 2001. You take the first and third digit as the month: 01 means January and you take the second and forth digit as the year: 01 means 2001
Serial number "LA0999" means the bag is made in USA on 09 (means September, take first and third digit), year 1999 (take second and last digit 99 meaning year 1999, only last 2 digits of the year is displayed for simplicity)
Now what do you think serial number "CA0917" mean? Yes, your right, it means Made in Spain, January 1997.
Since January 2007, Louis Vuitton has yet adopted another serial number reading system. Instead of first and third digit being the month, it now means the week of the year the bag was made.
For example, VI 2007 translates "Made in France 20th week of 2007 meaning around the third week of May. This was perhaps changed to combat the counterfeit market.
Now that you are an expert in reading Date code or Serial Numbers, I will continue to show you more ways to buy 100% Authentic Louis Vuitton. :)