[ntp:questions] How to keep fake time in past/future?

unruh unruh at wormhole.physics.ubc.ca
Sat Apr 30 15:50:24 UTC 2011

On 2011-04-30, Joseph Gwinn <joegwinn at comcast.net> wrote:
> In article <slrnirllcv.g22.unruh at wormhole.physics.ubc.ca>,
>  unruh <unruh at wormhole.physics.ubc.ca> wrote:
>> On 2011-04-29, Cristian Seres <cristian-2 at contrasec.fi> wrote:
>> > Hi!
>> >
>> > How would you implement an NTP server which would need to offer a time 
>> > set deliberately in past/future, say 365*86400 seconds, or even better - 
>> > first set the freely chosen date on NTP server and then keep the hours, 
>> > minutes and seconds in sync with the real time?
>> >
>> Perhaps you could tell us why in the world you would want to do that?
> It's very common, actually.  For instance, in Air Traffic Control they 
> record everything, and later play prior events back, to figure out what 
> happened.  
> Alternately, very large and complex training scenarios are written, the 
> scenario happening at some time different from the present, perhaps 
> past, perhaps future.

And why do we not hear from Seres who could tell us why, instead of us
all guessing here. Any of the guesses I have seen have been trivially
satisfied by simply killing ntpd and resetting the computer's clock. The
OP wanted the milliseconds to be right, but the days or years wrong. 
Or if you want set up one computer with LOCAL clock as only source, and
set the the inappropriate time, (without any other source of time) reset
the clock and have the others use it as their server. But of course the
milliseconds will not be right. But why are we not hearing from the
person who presumably knows why they want their computer clock
mistreated thus?

> Joe Gwinn

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