Thursday, December 22, 2011

Four Years Since Surgery

Lunar Eclipse (Nasa.gov)
Courtesy of the US Naval Observatory Data Services, yesterday was Julian Day Number 2455916.5 . The Julian date for CE 2011 December 21 00:00:00.0 UT is JD 2455916.500000. The JDN, or JD, is simply the count of days since a given day in the past .  The year, month, day of month conversion is more complicated since the number of days in a solar year is 365.25 - 0.0078103 (J2000) and different from the fixed star frame sidereal year  of 365.25 +0.006363004, as of J2000). days. Subtracting  the JDNs  of two calendar dates gives the number of days between those dates. Of course, one must have an accepted algorithm for converting from calendar dates to JDNs  (and back). 

The official date of my surgery was December 21, 2007  -  JDN 2454455.5 which gives 1,461 days since surgery.   Since 1, 461 modulo 365 is one,  there was a leap year somewhere along the survival curve. :)  

Today, the winter solstice  occurs at 05:30 UTC.  In 2007 it occurred 06:08 UTC.    Happy Survival Day...the days get longer for the next 6 months or so - nice thought. 
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