Do you mean, that you dont understand, how someone can play well, because its night? First of all its not night everywhere at the same time. So maybe they are just in a different time zone than you. And besides professional poker players might sleep at odd hours, depending when they prefer to play. This is not any different from people working the night shift in a factory. I am not a professional, and even I sometimes start playing at 3-4 am in the morning. But then I have already slept, so I am actually more rested, than if I play later in the day.