No one knows what time it will be. No one knows the hour when Jesus will appear. If Christ hadn't come the first time as a tiny baby on that first Christmas, we wouldn't know God, and our sins would not have been forgiven.
But because we know Jesus came to earth the first time, we can be sure He will keep His promise to come the second time and take us to Heaven to be with Him for ever – if we are born again and ready!