Do I claim for last year or this year?

I rang the benefits office 2 weeks ago to start claiming for working tax credit and child tax credit as I had a baby in February of this year.

The forms have arrived today and they are for the tax year 6 April 2012 to April 2013. Can I still fill these in or do I need a new tax form?

This is the first claim that I have made and wasn't entitled until this year.

(I know I could ring them and ask but I have very little credit on my phone!)