Dateadd and Datediff equivalent in Universe IDT

Hey experts

I am trying to create an indicator field in my Universe where based on a certain criteria for my date in the table, the indicator has some values.

My indicator  should say 'Y' if my date is in the last 12 months, 'P' if between 13 and 24 months and N otherwise.

Here is the screenshot of the sql formula I am using which works fine...

I have attached the screenshot because I cannot copy and paste in SCN forum ... don't know why!!

I have tried with 'timestampadd' function but cant seem to find the first day and last day of month equivalent ...

Here 

any ideas?

cheers