Baby can already tell the differences between light and dark while in the womb, but doesn't yet really have a day-night cycle.
A newborn baby isn't really "awake" more than 3 hours per day. The rest of the time they'll sleep and doze in and out. The amount of time they're awake gradually increases over time.
After about 4 or 5 weeks, they'll develop a sleep pattern, but it may take up to 16 weeks before they fall into a 24-hour cycle.
Learning a proper day and night rhythm
With these tips hopefully baby will soon fall into a nice 24hr rhythm before too long.
From angelababy In Q&A