I slept, how should I respond to the professor?
Students are allowed to sleep at night. In all likelihood the prof just forgot about the differences in timezone, or miscalculated the time difference.  Just answer something like :

Dear prof. XXX,

Sorry I missed your reply. It was 22:00 hours when I sent that message, and went to sleep immediately afterwards. Could we make another Skype appointment?

Best,
YYY