[LEAPSECS] Common Calendar Time (CCT) -Brooks Harris

[Brooks Harris]

On 2014-01-18 08:02 AM, Joseph Gwinn wrote:

> POSIX time is defined without reference to NTP, which is its own world

> with its own standard.  Note that the NTP standard, RFC-1305, is dated

> March 1992, which is well after the first POSIX standard (1988 - the

> Ugly Green Book).  Nor does NTP have any reference to UNIX or POSIX.


Yes it does.

Figure 4: Interesting Historic NTP Dates of NTP refers to "First day 
UNIX" and locates it 63072000 seconds before 1972-01-01T00:00:00Z (UTC)-

+-------------+------------+-----+---------------+------------------+
    | Date        | MJD        | NTP | NTP Timestamp | Epoch            |
    |             |            | Era | Era Offset |                  |
+-------------+------------+-----+---------------+------------------+
    | 1 Jan -4712 | -2,400,001 | -49 | 1,795,583,104 | 1st day Julian   |
    | 1 Jan -1    | -679,306   | -14 | 139,775,744   | 2 BCE            |
    | 1 Jan 0     | -678,491   | -14 | 171,311,744   | 1 BCE            |
    | 1 Jan 1     | -678,575   | -14 | 202,939,144   | 1 CE             |
    | 4 Oct 1582  | -100,851   | -3  | 2,873,647,488 | Last day Julian  |
    | 15 Oct 1582 | -100,840   | -3  | 2,874,597,888 | First day        |
    |             |            |     |               | Gregorian        |
    | 31 Dec 1899 | 15019      | -1  | 4,294,880,896 | Last day NTP Era |
    |             |            |     |               | -1               |
    | 1 Jan 1900  | 15020      | 0   | 0             | First day NTP    |
    |             |            |     |               | Era 0            |
    | 1 Jan 1970  | 40,587     | 0   | 2,208,988,800 | First day UNIX   |
    | 1 Jan 1972  | 41,317     | 0   | 2,272,060,800 | First day UTC    |
    | 31 Dec 1999 | 51,543     | 0   | 3,155,587,200 | Last day 20th    |
    |             |            |     |               | Century          |
    | 8 Feb 2036  | 64,731     | 1   | 63,104        | First day NTP    |
    |             |            |     |               | Era 1            |
+-------------+------------+-----+---------------+------------------+

                  Figure 4: Interesting Historic NTP Dates


My reading of this is the table is actually normative - there's no 
indication it is informative except the table's title. In any event, 
Mill's intention was clear, and gives us the crucial standards-based 
link between UTC and the Unix/POSIX "origin", or "the Epoch".

[ --------
Caution - Michael Deckers pointed out in an earlier email on the list 
(good catch!)-

   Please note that this table has to be read with caution.

   Besides the typo -678,491 for -678,941, one has to realize that
   "1 Jan -4712" is meant as a date in the Julian calendar, but
   all the other dates in column 1 must be taken as Gregorian calendar
   dates, even those before 1582-10-15 -- else the entries in
   columns 2,3,4 become incorrect. And this makes the entry
   in column 5 for the date 1582-10-04 incorrect.
------- ]





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