Thoughts on the Leap Day and the English Tax Year

published: Sun, 29-Feb-2004   |   updated: Thu, 27-Oct-2005

It's kind of late, I've just cooked a Chicken Biryani, we had a not-very-good Californian Merlot (at least the alcohol is kicking in), and it's leap day. And so it's time for a fascinating question: what does the leap day have to do with the fact that the English tax year runs from April 6 to April 5 of the following year? Read on and find out.

Let's tell a little story, maybe several little stories, all inter-related. The first concerns yours truly. My parents are fond of telling me that my birth cost them money. Why? Because my birthday is April 6. I was born right at the start of the new tax year. My parents were unable to claim for me in the previous year, unlike my brother-in-law who was born on April 5. So, right from the get-go, I cost Mum and Dad money; they'd be the first to tell you I've cost them ever since.

Another little story. Whatever Julius Caesar may be famous for, and the fact that my parents named me after him for some unknown reason, he is most well-known for imposing the Julian calendar. Well. all right, he's famous for the "Et tu, Brute" line, but that was a little later than my story. By 46 B.C.E., the calendar was in a bloody awful mess. The priests were in charge of it and were well known to accept a little cash under the table to fiddle with it. They'd increase the length of a year for politicians they liked, and decrease it for those they didn't like, to make the popular ones stay in longer.

Caesar was in a quandary: the calendar was a massive 90 days adrift from the seasons. Yes, 90 days; so much fiddling had been going on. With the help of an astronomer called Sosigenes, he decreed that 46 B.C.E. was to have the extra 90 days tacked on the end to make everything right again (that year became known as the Year of Confusion), and then from 45 B.C.E. Things Would Be Different. Every year would have 365 days, divided up into the 12 months, but every fourth year would have 366, with the extra day added in February. For some bizarre reason, he decided that the extra day would appear between February 23 and 24, but at least he was on the right track. 45 B.C.E was to be the first leap year in this new Julian calendar.

Incidentally, a leap day is known as the bissextile day and a leap year as a bissextile year. The reason? Another little story. The Romans didn't count the days in the month from the first of the month, they counted backwards from certain days in the month. These special days were the Kalends (from which we get the word calendar, as it happens), the Ides and the Nones. The Kalends was the first of the month, The Ides was either the 13th of the month or the 15th of the month (for months with 31 days, March, May, July, October, the Ides were on the 15th). The Nones were 9 days before the Ides. (And, of course, we know that Julius Caesar had to beware the Ides of March; that is, the 15th of March). So, anyway, Caesar decreed that the extra day would be a duplication of the 6th day before the Kalends of March. Since, in those days, February had 29 days, that meant that the 24th February (our counting) would be duplicated. Duplicate in Latin is bis, and 6th is sextus, hence the word bissextile.

(By the way, of course, the Romans didn't think of the year as 45 B.C.E. They thought in terms of years since the foundation of Rome. 45 B.C.E. was 709 A.C.U. (ab urbe condita).)

Anyway, back to Ancient Rome. Julius Caesar was assassinated on March 15, 44 B.C.E. Naturally, he wasn't around to see that the officials in charge of the calendar screwed it up and made every third year a leap year instead. (Was this the first off-by-one bug?) In fact, it wasn't until Augustus became Caesar that the calendar was put right again. Several leap years were dropped to cater for the extra ones added in by the officials, and everything got on track again by 1 B.C.E., which was a leap year.

Another story. By 1582 C.E., the fact that the Julian Calendar approximated the tropical year as 365.25 days, whereas the true value was 365.2422, meant that once again the calendar was adrift from the seasons. Pope Gregory XIII decreed that the calendar would have an adjusting factor: skipping 10 days. He also instituted a new rule for the calendar. The rule was, if the year were divisible by 4 it was a leap year, unless it were divisible by 100, in which case it wasn't, unless it were also divisible by 400, in which case it was. Got that? This approximated the tropical year to 365.2425 days; pretty good but in another 1,500 years we might have to fiddle it again. Pretty much all Catholic countries followed suit, eventually. The English, though, said, no way, and continued to use the Julian calendar.

Final story. By 1752 C.E., the English finally realized that the Gregorian calendar wasn't really a nasty popish plot to undermine them and did actually make sense. By this time, the Julian calendar was 11 days adrift from the seasons. So, by Act of Parliament, Wednesday September 2, 1752, was to be followed by Thursday, September 14, 1752. Not only that, but the Act decreed that from now on January 1 was to be the first day of the year. You see, up until then the Brits had been counting March 25 as the first day of the year (oh, those wacky Brits).

Mass hysteria. Not only did the populace believe that government was somehow stealing 11 days, but that they would be taxed for a full year having only done about 9 months work.

You see, taxes were due on the first day of the new year, March 25. If the new New Year was to be January 1, they would have worked from March 25 to December 31, minus the 11 days the government had stolen, a grand total of 282 days, yet they'd be asked for 366 days worth of tax (1752 being a leap year).

Let's get this right. The year 1751 C.E. in England (and America as well, for that matter) went from March 25 to March 24. If we, from our 2004 viewpoint, were counting, it's as if our January 1, 1752 was called January 1, 1751. 1752 for my forebears only started on March 25. Our February 1753 was their February 1752, and thus had 29 days since 1752 was a leap year. Parliament was, in essence, decreeing that the year 1752 was to run from March 25 to December 31, minus those 11 days it had taken away in September.

So the government bowed to the pressure and allowed for the tax year to go from March 25, 1752 to March 24, 1753 (new style; old style, it was still 1752 of course). However, because of the 11 days that were jumped over in the shortened month of September 1752, the end date was moved to April 4, 1753. Also the population was also missing a leap day: the old style calendar had a February 29 since 1752 was a leap year, but that day had disappeared since the February now fell into 1753. So the end of the tax year was made April 5, 1753, and the new tax year started on April 6, 1753. And, believe it or not, Parliament never changed it from then on. Hence, in England, the tax year runs from April 6 to April 5 to this day.

Which is where we came in. "Time for bed," said Zebedee.