I have tried to import a CSV file i created from MS Project task list and keep running into an issue with dates.
I was originally having issue with the date format until i looked at the text version of csv. The format in the CSV file dd-MMM-YYYY
Once i was able to clear the errors form the import. I looked at the task and the dates are not correct.
I mapped the Submitted dated date to Date Created and Due Date to Due Date.
I did not use Custom Fields.
Here is an image of date section in the task, it is making everything 27/DEC/20 and screen shot of the dates from the csv file. I know the dates are in the past but it is putting the same date for all even the ones in the future.

