What is the history of Tax Day in the United States?

Tax Day exists as a deadline for many United States residents to report earnings in order to pay income taxes.

The United States introduced the income tax in 1861 in order to fund the American Civil War. This was later deemed unconstitutional and repealed in 1872. This was later reenacted in 1894 as part of the Revenue Act with its constitutionality settled in the Sixteenth Amendment to the Constitution in 1913. Tax day was initially set for March in 1913 and was eventually moved to April 15th in 1955.