13 September 2006

Birthday math

I was planning on posting about turning 30 at the time I was born, 01:29, but I fell asleep too early.  I woke up around 08:00 and quickly posted, then changed the post time to 01:29.  Cool.

But today I started wondering when exactly I really turned 30.  I mean, birthdays don't take leap years into account.  There are 97 leap years every 400 years, because a year is a leap year if it's divisible by 4 unless it's also divisible by 100, except that years divisible by 400 are leap years.  For example, 1900 was not a leap year but 2000 was.  So the number of days per year on average is (303 * 365 + 97 * 366) / 400 = 365.2425.  Multiply that by 30 to get 10957.275, the number of days between my birth and the moment I really turned 30.  There were 7 leap days between 9 September 1976 and 9 September 2006, giving 10957 calendar days total.  So I really turned thirty 6 hours and 36 minutes (0.275 days) after my birth time of 01:29, or 08:05, which is coincidentally about the time I posted anyway.

From now on I'll be honest about my post times.


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