Correct conjugation of souvenir de

Question

Hello,

I'm hoping you can clarifying something.

I had to translate the following sentence to French:

This year I remembered her birthday for the first time

I used:

Je me souvenais s'anniversaire pour la première fois.

I was told this conjugation was incorrect and I had to use "je me suis souvenue".

I don't understand why?

Thanks in advance.

Accepted Answer

Apart from needing to be "se souvenir de" in all cases
 https://progress.lawlessfrench.com/my-languages/french/view/812?rts=%252Fsearch%253Fs%253Dsouvenir%252Bde 
this is a matter of choosing between imparfait or passé composé. The episode described is a single episode of 'remembered her birthday', 'for the first time', 'this year' - passé composé. 
However, if you are the "Je", not 'je me suis souvenue' but 'je me suis souvenu' (de son anniversaire) would seem likely to be correct !