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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