Who is this "little horn" in Daniel, when did he come, what did he seek to change?

Daniel 7:24-25 GNB The ten horns are ten kings who will rule that empire. Then another king will appear; he will be very different from the earlier ones and will overthrow three kings. (25) He will speak against the Supreme God and oppress God's people. He will try to change their religious laws and festivals, and God's people will be under his power for three and a half years.