You’d think a person could take a day off today.After all, in most years this busy old world manages to get a year’s worth of work done in 365 days, even with the standard allotment of weekends, holidays, personal days and goofing-off days.You’d think 365 days would be sufficient for this year’s business, too, and when a whole extra day — today — falls in our lap, we could all just kick back and enjoy it.And yet, as you can see, here I am.All over town, across the country and around the world, noses are pressed to grindstones just as on any other weekday workday. We wait four years for leap year, and when our bonus day arrives, we leap out of bed and trudge off to work.What gives?Well, it turns out that this, too, is part of the great eternal plan.The Gregorian calendar, the one we use, was devised in 1582 as an improvement on the old Julian calendar. The new system was designed to keep our earthy calendar aligned with the solar year.The extra day every leap year reflects the fact that the Earth actually takes 365 days and almost (but not quite) six hours — a standard calendar year plus one-quarter of a day — to complete its annual journey around the sun. So we accumulate nearly an additional 24 hours every four years.To balance the books, we get a leap year every year that’s divisible by four, except for “century years” that are not divisible by 400. That means 1600 and 2000 were leap years, while 1700, 1800 and 1900 were not.Every leap year, we collect our extra day on Feb. 29, the date that doesn’t exist in other years.Some strange things have happened on leap day. In 1504, Christopher Columbus used advance knowledge of a lunar eclipse to frighten hostile natives into providing food for his crew.The most pervasive leap day tradition — though probably of decreasing relevance in our modern society — is that Feb. 29 is a day for women to reverse traditional roles and propose to their boyfriends.People born on Feb. 29 have a chance to live to an advanced age without the fire hazard of all those candles on the cake. On the other hand, every birthday is an excuse for unleashing four years’ worth of pent-up celebration.But for those of us who aren’t celebrating a birthday today, Feb. 29 is just another day.Because as it turns out, in the great scheme of things leap day is most likely to fall on a Monday or a Wednesday; next most likely on a Friday or Saturday; and least likely on Sunday, Tuesday or Thursday. In other words, more likely on workaday Friday than on a leisurely Sunday, and more likely on a blue Monday or hump day Wednesday than on a free and footloose Saturday.Doing a little checking, I find that I’ve been luckier than the law of averages calls for. There have been 10 leap days since I began working, and as near as I can figure I’ve worked seven of them. That means I’ve had the day off 30 percent of the time, as opposed to 28.6 percent of the time during a typical, random week with five workdays and a two-day weekend.Of course that kind of luck can’t hold. If I work 400 years — the time it takes for the Gregorian calendar to cycle through all of its permutations — and if the Earth remains in more or less its current orbit, a disproportionate number of my leap days will fall on Mondays, Wednesdays and Fridays, and relatively fewer of them on Saturdays and Sundays. Figuring that leap day — unlike your arbitrary, generic weekday — never lands on a holiday, the cosmic likelihood of getting a day off on Feb. 29 is reduced even further.The workdays just stretch on into eternity.