[ntp:questions] Refclock Oncore Driver Change

Terje Mathisen terje.mathisen at tmsw.no
Wed May 8 20:58:24 UTC 2019

Jakob Bohm wrote:
> Maybe (later) have a general setting (usable by all clock sources) to
> specify "known minimum date", thus establishing windowing for all of the 
> following:
>    The NTP epochs (2**32 seconds, epoch 0 starts at 1900-01-01Z)
>    32 bit unsigned Unix epochs (2**32 seconds, epoch 0 starts at 
> 1970-01-01Z)
>    31 bit Unix epochs (2**31 seconds, epoch 0 starts at 1970-01-01Z)
>    GPS epochs (1024 * 7 * 24 * 3600 seconds, epoch starts at 1980-01-06 
> 00:00:19 TAI)
>    two-digit time sources epochs (100 years, epoch 0 starts at 1 BC-01-01Z)
>    TOD-only sources (system TOD chip without calendar part).
>    NT-time epochs (2**63/10**7 seconds, start at 1601-01-01Z)
>    MS-DOS time epochs (128 years, start at 1980-01-01 local)
> Such epoch settings could include ntp.conf options for
>    Absolute minimum date
>    Maximum time before time of an arbitrary disk file.
>    Maximum time before last persistently recorded good NTP timestamp.
>    Maximum time before current NTP time estimate (after filtering).

Having a known minimum date would be fine, the modification time of 
ntp.conf could be used, or as you suggest, a new generic "epoch-start 
yyyy-mm-dd" option in the conf file.

Any driver with potential epoch wrap around risk could then use this 
value to sanity-check the calculated date.


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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