How does Linux handle DST/ST? It's all about time...

Bruce Labitt bruce.labitt at myfairpoint.net
Tue Nov 10 14:14:58 EST 2020


"Dumb" machine, while actually computer controlled, is closed source.  
No possibility of changing its behavior.
No ssh, no network.  It's a data logger to an SD card.  I have to use 
sneaker net to transport data to my PC.

Other possibility (after a SD card backup) is to change the dumb machine 
clock back to standard time, hopefully without messing any settings up.  
Fortunately I have recorded all the necessary settings.  The dumb 
machine has big warnings to not do such a thing as the instructions warn 
of data corruption.

Probably will end up just changing the dumb clock.  There does seem to 
be a struct with an int called tt_isdst, which should be useful, 
however, not sure the solution would be platform independent.  As I 
understand it, linux uses UTC in the RT clock and Windows uses 
localtime.  How messy.  Oh well, so much for a sw solution, going to 
change the time on dumbo.

Back to what you all were doing... Sorry for the noise.


On 11/10/20 1:23 PM, Michael ODonnell wrote:
>
> You can mess around with DST and such but this slightly sleazy hack
> might serve an alternative: find some way to get your "dumb" machine to
> tell your "smart" machine what time it thinks it is currently, and then
> force the smart machine to that time.  For example, if SSH works from
> the smart machine to the dumb one then from the smart one you might say:
>
>   % x="$(ssh dumb date)"
>   % sudo date --set="$x"
>
> ...or some variation on that theme.
>
>    --M
>
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