If you were born on February 29 in a leap year, should you celebrate your birthday on February 28 or March 1 in a non-leap year?
An Australian judge has, kind of, weighed in on this age-old dilemma as she decided whether a teenager should be tried in a children's or adult court.
The case is about a teenage girl, known only as PM, born on February 29, 2000 – a leap year. She was charged in the Australian Capital Territory (ACT) with committing offences on February 28, 2018.
If you know your leap years, you will know that in 2018 there is no February 29. So before PM could go on trial, the court had to answer these questions: was she 17 or 18 at the time of the alleged offences, and, subsequently, should she be tried in the ACT Children's or Magistrates Court?
Chief Magistrate Lorraine Walker ruled in the Children's Court in March that PM was 18 at the time of the alleged offences and should be tried as an adult.
But PM appealed, and last week in the Supreme Court, Associate Justice Verity McWilliam ruled that she was actually not 18, she was 17, and should be tried in the Children's Court.
In the first decision in March, Walker had relied on caselaw (law developed by judges over time, as opposed to laws passed by politicians) that said a person "attains" an age at the start of the day before their birthday.
It differentiates between a "birthday" (the anniversary of someone's birth) and the day you "attain" an age (the day before your birthday).
In one case referred to by Walker, the judge wrote that this rule was "so lacking in rational foundation and is so out of touch with ordinary usage" that they wanted to change it to just be somebody's actual birthday, but didn't think they had the power to.
This clearly annoyed judge went on to lament: "I have reluctantly reached the conclusion that there is no escape from applying the rule to the attainment of any age and for any purpose unless the context in which the expression as to age is used indicates an intention to the contrary."
It was this caselaw Walker relied on to say, no, PM was 18 when she allegedly committed the offences. But on September 7, McWilliam overturned that decision on appeal in the Supreme Court.
At the appeal, the Director of Public Prosecutions (DPP) argued that PM was 18 when she allegedly committed the offences, using the definitions of "calendar month" (meaning one of the 12 months of the year) and "month", which means this, according to the judgement:
month means a period beginning at the start of any day of one of the calendar months and ending
(a) immediately before the start of the corresponding day of the next calendar month; or
(b) if there is no such corresponding day—at the end of the next calendar month.
The judgement then provided some examples of a "month", and honestly, I thought I understood what a month was but after reading this judgement I am not so sure.
"The period beginning at the start of 8 May 2014 and ending at midnight on 7 June 2014 is a month."
"The period beginning at the start of 30 January 2014 and ending at midnight on 28 February 2014 is a month. The month ends on the last day of February because in that year, February does not have a day corresponding to 29 January (because 2014 is not a leap year). If the period began at the start of 30 January 2016 (ie a leap year), the month would end at midnight on 29 February 2016."
The DPP argued: "Each year that the plaintiff has aged since 29 February 2000 is measured by the passage of 12 calendar months. Substituting the definition of 'month', because there is no corresponding day three out of every four years, the 12th month of every common year the plaintiff has been alive, concludes on 28 February."
This means PM was 18 on February 28 2018 because there was no corresponding day of February 29 that year, the DPP said.
But PM argued it's unhelpful to look at definitions of "year" and "calendar year" and that it's "a matter of logic" that a person with her birthday is not 18 on February 28, 2018, according to the judgement.
She contended that the word "birthday" should mean what we all think it means — the anniversary of someone's date of birth.
"[PM] relied on simple maths," McWilliam wrote. "Putting to one side 29 February, the anniversary of any other date occurs either 365 or 366 days after the date in question. To find that the anniversary of 29 February was 28 February would cause the anomaly that the anniversary occurs after only 364 days, which the plaintiff submitted would be an absurd outcome."
The DPP then said PM's argument was wrong, and even quoted from the bit in the Gilbert and Sullivan opera The Pirates of Penzance where Frederic, also born on February 29, is tricked into believing he only has a birthday once every four years:
"Though counting in the usual way, years twenty-one I’ve been alive,
Yet, reckoning by my natal day, I am a little boy of five!"
McWilliam ultimately decided that applying the "ordinary dictionary definition" of the word "birthday" was a more sensible route.
"In my view, it is unnecessary to resort to mathematical calculations of a year, or definitions of a 'month' in order to work out what a 'year' means," she wrote.
McWilliam pointed out that the ACT Legislation Act says "a person is an age in years at the beginning of the person's birthday for the age".
This word choice indicated a "deliberate intention" to move away from the idea that a person became a particular age on the day before their birthday, she wrote. It follows that PM was not an adult on February 28 because she hadn't reached the start of her birthday yet.
"It was only on 1 March 2018 that she became someone who was 'at least' 18 years old," McWilliam ruled.
So there you have it. Admittedly this ruling is based on legislation in the Australian Capital Territory and can't automatically be extended to other states and countries.
But if you're ever arguing with a friend about leap year birthdays and they insist it's February 28, feel free to tell them that according to the law, they are wrong.