Expression - First date and last date of current month, current year

Hi

I need to have 2 ssrs expression as I can use  as default parameters in my report where I can -  out from my Time dimension, get thefirst date of the current, current year - and one where I get last date, current month, current year.

My data source is a SSAS cube and my timedimension is structured like this:

Any suggestions how to solve this ?