I'm stuck. 
Please help! I'm having difficulty with the "set the close date to one month from today" portion.  I looked at a previous discussion and tried the suggested formulas - TODAY() +30, {!$System.OriginDateTime} +30, DATE(year, month+1,day), and DATE(YEAR(TODAY()),MONTH(TODAY())+1,DAY(TODAY())) yet I keep getting an error in my formula.
 

Hi Anybody, who took the TrailHead. Visual Workflow challange, I am not able to change the close date of the Opportunity by adding 30 days to it.

{!$Flow.CurrentDate} + 30 does not let me save.

thanks in Advance
Amitabh