[LEAPSECS] presentations from AAS Future of Time sessions

[Brooks Harris]

On 2014-01-13 09:29 AM, Michael Deckers wrote:

>

>   On 2014-01-12 03:28, Brooks Harris quoted from RFC 5905:

>

>> Then, and very importantly,  Figure 4: Interesting Historic NTP Dates

>> states the relationship to "First day UNIX" -

>>

>>  +-------------+------------+-----+---------------+------------------+

>>  | 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            |

>>  +-------------+------------+-----+---------------+------------------+

>

>   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.

>

>   Michael Deckers.

>

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>

Oh dear!

I had "worked" the numbers after 1900 to confirm (a pain to do), and was 
suggesting this table as the normative the link between 1 Jan 1970-First 
day UNIX and  1 Jan 1972-First day UTC. I had not bothered to verify the 
earlier values, but its important.

I suppose Mills did this table. I'm sympathectic to how tricky it is to 
do and confirm these values. It also highlights why due-process is 
important - the better to catch mistakes like that.

-Brooks




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