Baby oversleeping?

My 7 week old (to my shock) slept from 9pm-5am. She woke up, got changed, and played with her dad for a little, then after I fed her, she fell asleep for one hour. Just fed her again and she's sleeping once more! It's kind of freaking me out. She isn't sick so it isn't that. She had a fussy day yesterday and didn't sleep all day. Could that be it? Did it ever happen to you? Is she just having a sleepy day? What are your thoughts?