Wednesday, March 2, 2011

When's your birthday time?

"February 29 birthdays" reminded us of the burden suffered by people born on February 29 when it comes to the question of when they may celebrate their birthdays. They have to decide between (1) aging only about one-fourth as fast at the people born the day before or after them and (2) having their own birthday cake seven times every four years.
    Well, the American Cerebral Liberties Union has come forth with a proposal for everyone to share the birthday burden. ACLU representative James Leland, Directrix, wrote me yesterday:
Age measures the number of years that have passed since birth. A year is the time it takes Earth to make one orbit around the Sun. So technically, your age increases by one year every time Earth is at the same point in its orbit around the Sun as it was at the time of your birth. The time this occurs each year would be your birthtime (b.t.) and the day on which your b.t. occurs would be your birthday.
    A year takes (roughly) 365.25 days, or 365 days, 6 hours to orbit the sun. (More precisely, it takes 365 days, 6 hours, 9 minutes, 9.7632 seconds.) So, for example, if you were born on 1/1/1971, at 9 p.m., your first birthday would have been on 1/2/1972 (b.t. ≈ 3 a.m.). Since 1972 was a leap year (it had 366 days), your second birthday would have been on 1/1/1973 (b.t. ≈ 9 a.m.). Your third birthday would have been on 1/1/1974 (b.t. ≈ 3 p.m.). Your fourth birthday would would have been on 1/1/1975 (b.t. ≈ 9 p.m.), and so on.
    But if you had been born at 3 a.m. on 1/1/1971, your first birthday would have been on 1/1/1972 (b.t. ≈ 3 p.m.), and your second birthday would have occurred the same year, on 12/31/1972 (b.t. ≈ 9 p.m.)!
    Directrix Leland notes that, "if you were born before 6 a.m. on 1/1, not only would there be calendar years in which you have two birthdays, but there would also be calender years in which you have no birthdays."

This is a very exciting proposal. I'm particularly encouraged by the prospect of a compelling new incentive's being injected into American mathematics education by which students would have to study more math in order to be able to calculate when their next birthday will be.
    It could revolutionize American education and help us catch up with the approximately ten countries whose students outscore ours in math. Write to your Congressperson today.
  1. March 3: Theological fallout from "birthtime"
  2. March 15: motomynd: "Quantity of life, or quality?"


  1. I can't remember where I put my car keys half the time. Knowing when my birthday will be, seems a little more complicated. Just so you know. I did have one last year, but not sure when it was (grin).

  2. Well, Steve, rest assured that James Leland, ACLU Directrix, intended the whole thing as a joke, as I did the original post on this topic. Also, I trust that you have figured out the true identity of that august individual? (Please don't reveal it in your comment; let me know by email. Thanks!)

  3. Could it be that the students of those 10 other countries are calculating their birthdays based on their birthtimes and the exact duration of the Earth's revolution? Probably not. There is likely another explanation for their success... and better remedies for the poor performance of our students.

  4. All the complex math is highly entertaining. May I contribute a simpler math situation that poses a similar conundrum?

    In what situation would you NEVER get to properly celebrate a birthday?

    Answer: Have one a week from Christmas, like mine.


  5. Mr./Ms. Anonymous, you are an excellent straightman/woman! Thanks!

    Mr. Motomynd, I'm familiar with the situation of which you speak. My daughter was born on December 31 (about 8 p.m., 1969). By the way, by ACLU Directrix Leland's method of determining birthday times, she would have had no birthday the following year. But because of the problem you identify, she wouldn't have really had it anyway (not to mention that, at that age, and never having had a birthday before, she wouldn't have been expecting one in the first place).