While April 15 might be a day most of us would like to forget, Uncle Sam won't let us. Thanks to the Constitution's 16th Amendment, Americans are required to take out their checkbooks each spring and write the IRS a whopper. April 15 is the cutoff date for when all tax returns must be postmarked and — since we're a nation of procrastinators — the deadline has come to be recognized as the official day to pony up. Officially set in 1955 — tax day was previously March 1 and March 15 — it has slowly become the most hated day in America.