Ok, in this case, the dates are right. Thank you for answer.
It is the manufacturing date.
I've bought two original cartridges, Magenta and Cyan, but I had problems with them (trace on paper), so I asked the shop to exchange them and they send me two news cartridges.
But, I don't understand what the date mean on the package, on the 2 "new" cartridges I have "18.9.07" and "17.4.21" (European format DD/MM/YY), and on the others packages I had stranges dates too...
Are these numbers really dates ? I join a picture it will be better than my poor English ;-)
Thank you for your answer.