This one isn't specific to the Columbian Exposition Half Dollar, but, IMO, it's an interesting historical twist regarding the World's Columbian Exposition itself.The traditional date for the celebration of Columbus Day in the United States was October 12 - US President Franklin Delano Roosevelt officially designated such in 1934 but it was considered the celebration date for many decades before.
When the US Congress set the date for the dedication of the Exposition grounds (via an Act of April 25, 1890), it did so for October 12, 1892 as it was believed at the time to be the 400th Anniversary date of Columbus "discovering" America. There was one little issue, however.
The October 12 date was established under the Julian Calendar, which had been proven inaccurate due to its miscalculation of the true length of a calendar year (i.e., the time it took for the Earth to complete an orbit around the sun which led to the seasons getting out of sync with the calendar); it was replaced by the more accurate Gregorian calendar. Due to its error, the Julian calendar did not accurately reflect many early American history dates. Great Britain, and her colonies, officially adopted the new calendar in September 1752. (As an example of the date issue, George Washington's birthday was originally considered to be February 11, 1731 under the Julian calendar, but was adjusted to February 22, 1732 under the Gregorian calendar).
In July 1892, Senator David Bennett Hill (D-NY) introduced a bill designed to change the dedication date from October 12, 1892 to October 21, 1892 - nine days later - the date according to the Gregorian calendar.
Hill's bill was "short and sweet":
Be it enacted, etc.,That the date for the dedication of the buildings of the World's Columbian Exposition is hereby changed from the 12th day of October, 892, to the 21st day of October, 1892.
After introducing his bill, Hill remarked "The act of Congress which became a law April 25, 1890 provided that the dedication of the buildings of the World's Columbian Exposition should take place on the 12th day of October 1892. There was some question raised at the time as to the propriety of that date. It seems to be now conceded that, strictly speaking, the date should be the 21st day of October according to our present calendar. The 12th day of October was according to the old system."
Hill also noted that New York had legislated its Columbus Day celebrations to take place on October 12th: "It has been proposed since the passage of that act [Federal] that there should be celebrations throughout the country in honor of the discovery of America by Columbus. They are to be held in different parts of the nation. Great preparations have been made in the State of New York for a celebration to take place in the city of New York on the 12th day of October next. That date was fixed by an act of the Legislature of the State of New York and an appropriation has been made for the celebration. The Legislature has adjourned. It can not well be reconvened. That celebration would conflict to some extent with the dedications of the buildings in the city of Chicago."
Hill then let his true motivation for his bill be known: "It has now been proposed that the date for the dedication of the buildings at Chicago should be changed. It is desired by the managers on the part of the State of New York that this should be done. It is desired by the citizens of the State of New York. The celebration at New York will be simply a preliminary one to the grand celebration at Chicago. It will attract attention to the one at Chicago. It will certainly aid the one at Chicago. The citizens of New York, especially the public officials of that State, desire to participate in the opening of the Exhibition buildings at Chicago, which they can not well do unless the date is changed."
So, under the veil of "historical accuracy," Senator Hill was looking to clear a New York-based scheduling conflict. Had New York not already legislated October 12th as the day to celebrate Columbus, it's likely no bill seeking a change to the date of the Exposition grounds' dedication would have been introduced. Ah, the power of a local constituency!
The bill was passed in the Senate without objection and sent on to the House of Representatives. Upon receipt, the House referred the bill to the Select Committee on the Columbian Exposition. The Committee reported the bill favorably and it subsequently passed without issue in the House. US President Benjamin Harrison signed the bill into law on August 5, 1892.
As a result, the Exposition's dedication ceremonies were moved to October 21, 1892. The Exposition did not open after the dedication ceremonies were completed, however. The Exposition did not open to the public until May 1, 1893 as more time was needed to complete construction and prepare exhibits.
1892 World's Columbian Exposition Half Dollar - Christopher Columbus

For other of my posts about commemorative coins and medals, including other Columbian Exposition stories, see:
Commems Collection.