Can your baby distinguish day and night?

I know every baby is different. Mines just turned 7 weeks today and lately she's been wide awake every morning 8am-12pm sometimes 4pm she doesn't want to sleep! Take her a bath at 8pm But it's ok since she's been sleeping at night better then her first few weeks (tiring) I wake her every 3 hrs to change her diaper (sometimes she just goes back to sleep while I change her) and make her 3 oz incase she's hungry and of course she open her eyes and drinks if she is but goes back to sleep. I do that because if I wait for her to wake. She fusses a lot and is harder for me to make her milk and change her (since she turns purple when she cries and is my fear because she than starts having this weird breathing like from crying to much and to long)