What is the longest ratification period for an amendment to the United States Constitution?

Amendment XXVII to the United States Constitution prohibits any law that increases or decreases the salary of members of Congress from taking effect until the start of the next set of terms of office for Representatives. It was submitted by Congress for ratification on September 25, 1789, but became part of the U.S. Constitution on May 5, 1992, completing a record-setting ratification period of 202 years, 7 months, and 10 days.