Without a twelve month calendar, people would not know how to meet up at the same time. People would say, see you in 218 days, and they wouldn't be able to plan far in the future. Without a number system, we could not pay for things, and without wheels we could not go anywhere and lots of technology would become obsolete.
Abraham Lincoln's assassination dramatically changed the Reconstruction era. Booth may have decided to act on his hatred after Lincoln endorsed giving the right to vote to African-American men who had served in the Union Army.
