It is true that there's no hard and fast rule for babies passing motion. When my dear son was about 1mth old he was passing motion 5 times a day. I had another friend whose baby was poo-ing every 4 days. But for both our babies, they're happy, active and drinking milk just fine. So if your baby is like that, most probably it's ok. And if your baby's usual stooling pattern is every 2days, then that makes it normal.
Can't remember which mummy provided this link. I think it's pretty useful. You might want to check it out.
Diaper Decoder - Stool Types, Baby Poop, Poop Colors & Abnormal Stool - Tips & Advice - Similac