Datetick - plotting question

I am plotting a dataset (ds1, 5x7) with dates in first column and data in rest. Why does the bar chart plot the x axis data one month ahead?

bar(ds1.dates,double(ds1(:,2:end)))
datetick('x','mm-yy')

[Laurens Bakker]

Could you show us your data, so that we can take a look at the values in ds1.dates?