On August 3 1492 He sailed from Palos Spain, and arrived on Oct 12, 1492 in the Bahamas. That means it took him 70 days. At least he didn't sail off the Earth!
Back then it was believed that the Earth was flat, everyone knew you couldn't sail around the world, you would fall off.
Christopher Columbus believed the world was round. He had a reason to believe it too. He had read in the Bible where God said, He sat on the sphere, (circle) of the earth. Columbus knew the Earth was round because God has said it was a sphere, a sphere is round like a circle. I thought you might like to know that. You can read about it yourself in the book of Isaiah chapter 40 verse 21 he wrote this in his journal.