What is the significance of November 15 the day of there meeting westing game?

November 15 is significant in "The Westing Game" because it is the day the heirs gather at Sunset Towers to hear the will of Sam Westing. This sets off a series of clues and challenges that the heirs must solve to inherit Westing's fortune. It marks the beginning of the mysterious and intriguing game that drives the plot of the book.