Current YTD print date

[cognos05]

Hi,
I have a requirement to show the below calculation in my report header.

Current YTD: 2014/07/01 - 2015/04/01                           
Prior YTD: 2013/07/01 - 2014/04/01                              
Current Month: 2015/04/01 - 2015/04/02   
      
I have to show these dates in my layout calculations.

I am using dimensional reporting and what calculations should i use in my layout calculations to get the current YTD.

Thanks,
Nithya