How to use multiple date fields in a stacked bar chart

Hi,

Can anyone help me to point mulitple dates on a stacked Column/bar chart???
like date1 should be displayed in one color and Date2 in another color. when iam trying to do that iam getting error( like for the second date if i give 4/20/2010 it is taking like 4/20/2310).. I don't know how and why it is happening...

Thanks
Sowmya