Oh, you mean <span style="text-decoration: underline;">that</span> sort of date...
I tend to remove the cover and look at components, they are often date marked inside - inlet solenoid valves in particular often have a manufacture date stamped on them. Also sometimes the detergent dispenser casing might be date-stamped, or the drain pump, just look around under the hood for date stamps. It's very common to have date-stamped components.
Hi there to date zanussi aeg and Electrolux group washers there is a sticker at the bottom of the door you focus on the first 3 digits of the serial number
Digit 1 is the year of production
Digit 2 and 3 is the week of the year it was produced
Hope that helped you