On Sept. 9, Queen Elizabeth II will become the longest reigning British monarch, surpassing the record held previously by her great-great grandmother, Victoria, who reigned for 63 years, 216 days. Victoria became Queen June 20, 1837 and died Jan. 22, 1901. Allowing for leap years and the time of day at which each monarch was told of the death of their predecessor, it has been calculated that Queen Elizabeth will pass that landmark time at around 5:30 p.m. in the U.K. — or 12:30 p.m. EST. Elizabeth II became queen on the death of her father, George VI, Feb. 6,...