Septennial Act 1716 It did not require parliament to last for a full term, but merely set a maximum length on its life. Most parliaments in the remainder of the eighteenth century did indeed last for six or seven years, with only two lasting for a shorter time. In the nineteenth century, the average length of a term of the Parliament of the United Kingdom was four years. One of the demands of the mid-nineteenth century Chartists—the only one that had not been achieved by the twentieth century—was for annually-elected parliaments. The Septennial Act was amended on 18 August 1911 by of the
Metonic cycle based on the tropical year and maintain the seasons at the same calendar times each year. Nineteen tropical years are about two hours shorter than 235 synodic months. The Metonic cycle's error is, therefore, one full day every 219 years, or 12.4 parts per million. Note that the 19-year cycle is also close (to somewhat more than half a day) to 255 draconic months, so it is also an eclipse cycle, which lasts only for about 4 or 5 recurrences of eclipses. The Octon is of a Metonic cycle (47 synodic months, 3.8 years), and it recurs about 20 to