date set to 02 Janv. 0101

[frederic]

On windows 7 - Calibre 2.8 64bit

I add a book in PDF format by a drag and drop in the calibre windows
I want to modify the metadata and I can observe that the date is set to 02 Janv. 0101.

If I try to erase it with clic on green button => no effect
If I try to remove by inserting spaces, when I moving to an other field, the same date of 02 Janv. 0101 appear
If I try to select with the drop down list an other date and change the field => 02 Janv. 0101 comes again.

Find attached screen copy

Thanks
Frederic