Good Wednesday

Two days before Easter we observe Good Friday as the day on which Jesus was crucified. For anyone who is familiar with Jesus’ predictions about his death and resurrection this raises a problem. He said that just as Jonah was in the belly of the fish three days and three nights he would be in the earth three days and three nights. But how could this be if he was crucified on Friday and resurrected on Sunday?  Friday, Saturday, and Sunday make up three days but there are only two nights.