On 2/13, Joel Ewing wrote: "Astronomers are a perverse lot for
choosing an epoch origin at noon rather than midnight...".
This sounds biblical: "The evening and the morning were the first day.".
Confusion between noon and midnight and as to what day midnight
belongs to are endemic to the 12-hour clock. PanAm used to have a
midnight flight leaving Fairbanks, AK for the south 48. They avoided
the day ambiguity by calling the departure time 11:57.
Cocoa on the Mac has the primitive "TimeIntervalSinceReferenceDate"
which gives the date/time as the number of seconds since "the first
instance of Jan 1, 1900 returned as a double-precision floating-point
number, which gives millisecond precision with dates 10,000 years
apart (in either direction from 1970). It also recognizes the
different dates at which different localities adopted the Gregorian
calendar. However, the NSDate Class is not synchronized with leap-
seconds (International Atomic Time).
Dale Miller
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