Day 10,000: May 18, 1995



   Q.  I received the following from one of my mailing lists.  Does this
       affect us?  "...For those of you whose computers store dates as
       internal integers, we were recently reminded that May 18, 1995 is Day
       Number 10000.  From September 26, 1970 to the present, date numbers
       have been 4-digit representations.  But, now we have a five-digit
       number...."

   A.  By now you know that the VAX did not melt down when the calendar page
       turned to May 18, 1995.  The problem discussed on your mailing list is 
       not applicable to VAX/VMS systems such as ours.

       The VMS operating system does not store dates as offset from
       September 26, 1970.  In fact, VMS represents time as hundreds of
       nanoseconds offset from the Modified Julian Base Date of November 17,
       1858.  This is sometimes also referred to as the Smithsonian Base
       Date since it was adopted for satellite tracking in 1957 after the
       launch of Sputnik.

       Given this base date and a 63-bit absolute time representation, VMS
       is capable of keeping time from now until about 2:48 a.m. on July 31
       in the year 31,086.  In practical terms, however, the time display
       and manipulation routines currently available allow only a maximum of
       four digits to represent the year.  But, that still gives us until
       December 31, 9999 -- a little over eight thousand years from now --
       before we have to worry.


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