From the Harvard Gazette; It was completely arbitrary. March 4 was the date when officially the first Congress held its first meeting, and so that was taken as the zero point. April 30 happened also arbitrarily because it took that long, frankly, for people to get to New York from God knows where, by cart and the like. That’s how it was decided that March 4 would be the official date for the beginning and ending of terms. George Washington was a good sport. He didn’t say, “I get four years and four years should mean April 30.” He accepted March 4. And that’s how March 4 became Inauguration Day

1776 original inauguration day
mara lago has relevance as well
the actual property itself