29 February only occurs in years divisible by 4, and for centennial years, only in those divisible by 400. This little oddity has been written about in verse in that famous poem that has become a favorite mnemonic for remembering how many days each month contains:
Thirty days hath September,
April, June, and November;
All the rest have thirty-one,
Excepting February alone,
And that has twenty-eight days clear
And twenty-nine in each leap year.
29 February also figures prominently in musical theater in that Gilbert and Sullivan favorite, The Pirates of Penzance. In the G&S story, the hero, Frederick, through an unfortunate accident had been apprenticed to a pirate in his youth. He was slated to be released from his servitude on his 21st birthday. Alas, the lad was a leapling (one who was born on 29 February). Because of this unfortunate birth date, he wouldn’t have the 21st occurrence on the right date until he had lived for 84 years. The story of course doesn’t end there, but it takes a few interesting turns along the way.
There are also many more pragmatic issues associated with 29 February in the world of software. Julian Day 060, i.e., the 60th day of the year, occurs on 29 February in leap years, and on 1 March the rest of the time. This can serve to inspire many software tests to make sure that the accounting is correct. Of course the larger problem is at the end of a leap year rolling into the next year since there are 366 days rather than 365 before rollover should occur. The year 2000, the first centennial year since entering the computer age, was predicted to be the end of every computer system. Software engineers the world over prepared for the rollover into that year, across JD 060, and for the rollover into 2001. The world didn’t end, and although there were a few small hiccups in some systems, there was no worldwide computer shutdown.
Other concerns surround when to credit a birthday for leaplings in non-leap years. Does it fall in February the day before the date should occur, or in March, the day after? There is no real consensus in the leapling community for when to observe one’s birthday when there is no 29th in sight, and solid arguments can be made either way. Fortunately, a standard has evolved where official documents and events depend on one’s birthday to keep it in one’s birth month, at least in the US.
The real struggle for leaplings occurs when they reach what would normally be their eighth birthday as a child. For people born on every other day of the year, there is no confusion. Their birthday rolls around on the same day each year, and they get a year older. When one is young, these events are often cause for great joy as they get closer to being able to achieve various milestones in their lives. When one gets much older, the number of years tends to be less important, until they get to those decade milestone birthdays. But when a child reaches the age of eight, most of the people in their lives insist that no, they are only going to be two, and this can present a difficult obstacle. After all, what eight-year-old wants to be a toddler?
By the time a leapling approaches age 12, they start to enjoy the idea that they are only “3” and yet can do things a toddler could potentially only dream of doing, or more likely couldn’t even comprehend. After that, the game ensues for the rest of their lives.
Still, many milestones will occur on the wrong day, and quite possibly in the wrong month. Decade milestones only fall on 29 February every 20 years, rather than every 10 like they do for everyone else. And 29 February only falls on a Saturday every 28 years.
29 February is unique day. Be kind to the leaplings in your lives.