The deadline for filing federal income tax returns in the U.S. is midnight on the date of April 15 every year. Up until a few years ago, in every halfway large city in the country, you could see hordes of people attempting to fight their way into U.S. Postal Service buildings each April 15th as if there was a fire sale going on inside. Most of them wanted to be sure their income tax returns were postmarked prior to April 16. Traffic jams in those USPS parking lots frequently extended past midnight on the day in question.
In 1913 the 16th Amendment to the Constitution made the institution of mandatory income tax a fixture in the U.S. The amendment gave Congress legal authority to tax income and resulted in a revenue law that taxed individuals and corporations both. The fiscal year of 1918 saw those tax revenues exceed one billion dollars. What an enormous amount of money for those days. It might prove interesting to study the relationship between the first decade of income tax collection and U.S. participation in WW I. The very first federal income tax was levied to pay for the War Between the States.
In 1943 the withholding tax on wages came into being. Hmmm. What was the U.S. busy doing at the time? You guessed it. Taking part in WW II.
Humorously, in a bleak sort of way, tax acts signed in 2005 and 2006 were said to include incentives for individuals to save more for their retirement. This probably occurred at the same time retirement became an ever-receding date for most Americans without company pension plans or lucrative investments. Once it was an absolute given that women could retire at 62 and men at 65, with both beginning to collect Social Security benefits at those respective ages. Now it's become a question of whether we'll live long enough to retire at whatever increasingly distant age our government has decreed entitles us to collect our full benefits.
The Social Security Act was passed in 1935, during the Great Depression, to provide "compensation" to the unemployed, and to aid the needy, the elderly, the handicapped, and some minors. The 2 % tax was levied on the first $3000 of an employee's earnings. Half of it was paid by the employee and half by the employer.