It took nearly a year for the Constitution to fully go into effect -- after the necessary ninth state ratified it (New Hampshire, in June 1788), it was another three months before the irregularly-convened Continental Congress passed the resolution putting the Constitution into operation on September 13th, 1788.
Though many of the Constitutional Convention delegates were dissatisfied with the final product, deeming it a "series of unfortunate compromises", it is a document that has endured the test of time.
It has had barely two dozen amendments over its lifetime - one of those (XXI) repealing another (XVIII), and the first ten bundled into the Bill of Rights and ratified in 1791. And all Federal employees and military service members swear their oath to uphold and defend it -- *not* to any specific person or organization, but to the ideals expressed in this wonderful document.
Happy Constitution Day!