On 2014-01-18 09:29 PM, Tom Van Baak wrote:
Brooks,
Maybe I missed it way back in the thread, but can you give me an example why
you'd want a proleptic TAI or UTC?
I'm working on revising the names and a fuller explanation, but briefly -
The idea is to declare a 1hz timeline before 1972-01-01T00:00:00Z (UTC)
= 1972-01-01 00:00:10 (TAI). I'd called these "proleptic UTC" and
"proleptic TAI", but I agree, that's a bad way to explain it.
The purpose is to provide a scale so the exact offsets to some other
important timescales, such as NTP, POSIX, and 1588/PTP can be explicitly
declared. This is a contrivence for computational convenience.
I'm working on a revision of this table, which I posted earlier, but
perhaps this gives an idea what I'm trying to accomplish -
-----------------------------------------------------------------------------------------
Origin | UTC1972 | Coincides | UTC |Leap| TAI
Name | Seconds | with | |Secs|
| Offset | Origin of | ( Earth )
| | | (Correction)
| | | | |
-----------------------------------------------------------------------------------------
UTC1900 | -2272060800 | NTP | 1900-01-01T00:00:00Z | 10 |
1900-01-01 00:00:10
TAI1958 | -441763210 | TAI | 1957-12-31T23:59:50Z | 10 |
1958-01-01 00:00:00
TAI1970 | -63072010 | 1588/PTP | 1969-12-31T23:59:50Z | 10 |
1970-01-01 00:00:00
UTC1970 | -63072000 | POSIX | 1970-01-01T00:00:00Z | 10 |
1970-01-01 00:00:10
TAI1972 | -10 | UTC + 10s | 1971-12-31T23:59:50Z | 10 |
1972-01-01 00:00:00
UTC1972 | 0 | UTC | 1972-01-01T00:00:00Z | 10 |
1972-01-01 00:00:10
UTC1972_7_1 | +15724800 | First Leap | 1972-07-01T00:00:00Z | 11 |
1972-07-01 00:00:11
UTC1980_1_6 | +252892800 | GPS Epoch | 1980-01-06T00:00:00Z | 19 |
1980-01-06 00:00:19
-Brooks
/tvb
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