DateTime.Now.ToString("YYMMDD") into Label

I'm trying to pass a timestamp into a label  I already have one of the labels working correctly with this code:

this.lbl_time.Text = DateTime.Now.ToString("HHMM");

I would like to do this same for a lvl_date...  I thought it would be as simple as:

this.lbl_date.Text = DateTime.Now.ToString("YYMMDD");

Nope.  Any help?  Thank you again for your help!