Your first import where you map against name is correct, however Anaplan does not seem to recognize the date format you are importing. You can select the boolean next to start date and leave date (Custom Date Mapping) and then select the right mapping (M-D-Y). See screenshots below:
Once you have mapped them both correctly, you can run the import.
You do not need to fill in the Code when importing by Name. So the blank is not what is causing the issue here. Please check the Custom Date Mapping checkbox for both Start Date and End Date and use the MMDDYYY M-D-Y mapping. Regards, Anirudh
Just a quick heads up, the format Takamasa is using is M/D/YYYY, M/DD/YYYY, MM/D/YYYY and MM/DD/YYYY. The fixed format MMDDYYYY will not work for that as it will try to match it with each character as a string. The M/D/Y format as explained in the grey box will be able to deal with single or double digit months/days/years.