I took that photo above a couple of days ago (before getting some sort of cold/sore throat/cough from the lovely weather -- it's so backwards to get ill when the weather's warm and sunny...). About mid-afternoon. In the evening, some 5,5 hours later, I checked on them again and they'd already on those few hours begun to open up. That's the middle tulip you see in the photo above.
The next day they look like this.
Sometimes flowers grow really fast!