YOU SAID:
I was on my friends birthday
INTO JAPANESE
私は私の友人の誕生日にいた
BACK INTO ENGLISH
I was on my friend's birthday
INTO JAPANESE
友達の誕生日に
BACK INTO ENGLISH
On a friend's birthday
INTO JAPANESE
友人の誕生日に
BACK INTO ENGLISH
On a friend's birthday
Okay, I get it, you like Translation Party.