Having problem to import files from OO

I want to import tasks from OO with date information. I tried several kinds of format for the date column, (l attached them below) but none of them works. They all recognized as “metadata” and organized to “note”. Even I used “Copy/Paste” between these 2 apps, I got the same result. If I choose the “target filed” to “context”, not “due date”, no problem.
Can you give me some advise for the date format and help me resolve this problem?

format i tried:
3.16
3-16
3/16/2015
2015.3.15
10:00 pm 3-16
Tuesday March 17th, 2015 00:00:00.000
sunday
2015-04-07 10:00 +0000
2015-01-23 05:00:00 +0000
#03-16-15
03-16-15