You can check the build dates of a wide variety of Citroën models here: https://www.vindecoderz.com/EN/Citroen

Update:  Our apologies…  It appears that the website only works with a 17 digit VIN.  And even then the accuracy may be in question, particularly if trying to track Citroëns sold in the USA where cars were often sold as later model years because they were modified for export sales by third party companies like CXA and CINA.