How to add Time Series from 1998-2014 on the X axis using plotyy?

Hi all

I'm using plotyy to plot two data sets with the same x values over two different y scales. It all works perfectly, but the problem I can't add Time Series on X axis So How to add Time Series from 1998-2014 on the X axis.

this is the code

[Ax,H1,H2]=plotyy(X,ytr,X,ynd);
set(Ax,'xlim',[1 204]);
set(Ax,'xTick',[1:12:204]);
set(Ax(1),'YLim',[0 400]);
set(Ax(1),'YTick',[0:20:400]);
set(Ax(2),'YLim',[0 0.5]);
set(Ax(2),'YTick',[0:0.05:0.5]);

[dpb]

Is this another series in time or the same series you've already plotted as (apparently) against observation number?