Most people know that Queen Victoria is the longest reigning British Monarch. Many people also realize that Her Majesty, Queen Elizabeth II, is close to breaking that record. As current queen of 16 realms (Antigua & Barbuda, Australia, the Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, St. Christopher & Nevis, St. Lucia, St. Vincent & the Grenadines, Solomon Islands, Tuvalu, and the United Kingdom of Great Britain & Northern Ireland), she is expected to become the longest reigning British monarch of all time in less than a year.

However, people seem to have trouble specifying the exact time and date at which the length of Elizabeth’s reign will equal the length of Victoria’s. This article clears up the mysteries and calculates the exact date.

The first thing we need to clear up is when a British monarch’s reign begins. Some think it starts at the coronation ceremony. Some even think it starts when the monarch takes the oath. However, neither is correct. A monarch begins his or her reign the instant the previous monarch’s reign ends. This is usually due to the death of the previous monarch, which gave rise to the expression, “The King is dead. Long live the King.”

Victoria’s reign began at “about two in the morning” (according to Information Britain) on 1837.06.20 when her uncle, King William IV died. Her reign ended at 18:30 on 1901.01.22. She reigned for 63 years, 7 months, 2 days, 16 hours, and 30 minutes.

Elizabeth’s reign began when her father, King George VI, died. Unfortunately, no one knows the exact moment of his death. The 10:45 am announcement said only that he died “earlier this morning,” but at least one news story said “soon after falling asleep.”

Because we do not know King George VI’s time of death, and because King William IV’s time of death was stated as “approximately” two in the morning, we cannot state with any certainty exactly when the length of Elizabeth’s reign will equal the length of Victoria’s reign.

However, we can base our calculations on reasonable estimates and make note of the maximum error possible in each calculation.

We will start with Victoria. Her reign started at 1837.06.20 02:00 ± 2 hours (a reasonable best guess) and ended at 1901.01.22 18:30. These dates indicate that Victoria reigned for 63 years, 7 months, 2 days, 16 hours, and 30 minutes (± 2 hours).

We can now add 63y7m2d16h30m to the time Elizabeth began her reign. Or can we? In fact, this is where most people run into trouble with the calculation. They assume, incorrectly, that every year is the same length as every other year and every month is the same length as every other month. This assumption is obviously wrong. The only way to do the calculation properly is to calculate the number of *days* (not years or months) Victoria reigned, then to add that number of *days* to the date Elizabeth began her reign.

1837.06.20 02:00 to 1900.06.20 02:00 would be 22,995 days if all years were exactly 365 days long, but they’re not, so we have to add all the leap days (February 29th) that occurred within that range. Leap days occurred in 1840, 1844, 1848, 1852, 1856, 1860, 1864, 1868, 1872, 1876, 1880, 1884, 1888, 1892, and 1896 (note that 1900 was *not* a leap year), for a total of 15 leap days. Adding 15 to 22,995 tells us that there were exactly 23,010 days between 1837.06.20 02:00 and 1900.06.20 02:00.

1900.06.20 02:00 to 1900.07.20 02:00 is 30 days.

1900.07.20 02:00 to 1900.08.20 02:00 is 31 days.

1900.08.20 02:00 to 1900.09.20 02:00 is 31 days.

1900.09.20 02:00 to 1900.10.20 02:00 is 30 days.

1900.10.20 02:00 to 1900.11.20 02:00 is 31 days.

1900.11.20 02:00 to 1900.12.20 02:00 is 30 days.

1900.12.20 02:00 to 1901.01.20 02:00 is 31 days.

1901.01.20 02:00 to 1901.01.22 02:00 is 2 days.

1901.01.22 02:00 to 1901.01.22 18:30 is 16 hours and 30 minutes

We can now add up all those intervals (23,010 + 3×30 + 4×31 + 2 + 16h30m). Our conclusion, then, is that Victoria reigned for 23,226 days, 16 hours, and 30 minutes (± 2 hours).

Now it all seems simple enough. Just add 23,226d16h30m to the date and time of George VI’s death and that will tell us when the lengths of the two reigns are equal. However, as mentioned above, we do not know the time of George VI’s death.

The official announcement said George VI died “earlier this morning,” but a news story of that day said it was “soon after falling asleep.” The only thing we can say with certainty is it was sometime between 10:30 pm and 7:30 am (the time he was last seen alive and the time his body was discovered). For the purposes of our calculation, then, we will take the midpoint, 3 am, and we will again note the maximum error (± 4.5 hours).

1952.02.06 03:00 to 2015.02.06 03:00 is 23,011 days, including the 16 leap days that occurred in 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000 (yes, 2000 was a leap year), 2004, 2008, and 2012.

2015.02.06 03:00 to 2015.03.06 03:00 is 28 days

2015.03.06 03:00 to 2015.04.06 03:00 is 31 days

2015.04.06 03:00 to 2015.05.06 03:00 is 30 days

2015.05.06 03:00 to 2015.06.06 03:00 is 31 days

2015.06.06 03:00 to 2015.07.06 03:00 is 30 days

2015.07.06 03:00 to 2015.08.06 03:00 is 31 days

2015.08.06 03:00 to 2015.09.06 03:00 is 31 days

2015.09.06 03:00 to 2015.09.09 03:00 is 3 days

2015.09.09 03:00 to 2015.09.09 19:30 is 16h30m

Adding up those intervals (23,011 + 28 + 2×30 + 4×31 + 3 + 16h30m) gives us 23,226 days, 16 hours, and 30 minutes, exactly the same length we calculated above for Victoria. This tells us that the length of Elizabeth’s reign will equal that of Victoria’s at 7:30 pm on Wednesday, September 9, 2015 (± 6.5 hours).

It is still possible that the correct date is September 10th (because of the ± 6.5 hours), but there is a much greater probability that it will be the 9th.

Thy choicest gifts in store, on her be pleased to pour; long may she reign. May she defend our laws and ever give us cause to sing with heart and voice "God save the Queen."

*© Copyright 2011, 2014 by Warren Gaebel, B.A., B.C.S.. All rights reserved.*