It is no problem to import the .csv except the fact that the column “entered” is ignored. (I use the german translated phpList where it says “Spalte überspringen”)
The rows are correctly inserted - so I know there is no problem about the CSV itself - but the column ‘entered’ in the phplist_user is set to the actual date.
I’ve tried to name the column ‘googoo’ instead of 'entered" to force the system, to give me a choice via dropdown menu - but there is no ‘entered’ or ‘date of entrance’ I could take.
While you can’t overwrite the systems entered values with the old data you should be able to create a custom attribute (calling it “originally entered”, for example) and import your data into this field.