How does Linux handle DST/ST? It's all about time...
Bruce Labitt
bruce.labitt at myfairpoint.net
Tue Nov 10 12:01:32 EST 2020
Still looking at a time related bug. Wondering how (nowadays) linux
handles TZ and DST/ST transition.
Does linux embed DST state into TZ? Or is there a variable with a name
like "DST"?
I want to set two different machines, one a PC, the other a dumb
instrument to the same time. The dumb one doesn't do time adjustment.
My PC, obviously does.
I want to create a time, on my PC called: mytime = utc + utc_offset. If
utc_offset is invariant, then I am all set. All I can see is (at least
for ubuntu) there is TZ, which appears to be equal to utc_offset + DST*1.
If there was a variable called DST, I'd be done. Then mytime = utc +
utc_offset -DST*1, where DST=1 if now is daylight savings time, or DST=0
if now is standard time.
Anyone have insight on this? All I know is that my dumb machine was set
to DST last month. My PC is DST corrected. Half the time, (all during
ST) the device clock is ahead of the PC clock. Why is this bad - because
the PC refuses to read files timestamped in the future. I do not want
to correct the dumb machine's clock twice a year, as there is documented
potential for destroying data. This should be correctable on the PC
end, shouldn't it?
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