TeeChart:how to display dates

Hi!
I use TeeChart components to graph my data.
I create my series at design time but fill them with values looping through
a query result. On the X axis I want to display the date (TDateTime field).
I use the AddXY method to plot my data. The points are OK except that I
don't see the dates cccorresponding to my points. Why ?? I configure the X
axis as automatic and as of DateTime type..

Any help or suggestions are welcomed!
Thanks in advance
Lina