[ooni-dev] ooni-pipeline using local time zone when parsing timestamps

[Arturo Filastò]

> On Mar 17, 2016, at 19:40, David Fifield <david at bamsoftware.com> wrote:
> 
> I don't understand your explanation that "utcfromtimestamp() leads it to
> actually being converted back into the local timezone." That's what I
> would expect of fromtimestamp, not utcfromtimestamp. Consider these:
> 
> # fromtimestamp gives different values according to TZ:
> $ TZ=America/Denver python -c 'import datetime; print str(datetime.datetime.fromtimestamp(1458239719))'
> 2016-03-17 12:35:19
> $ TZ=Europe/Rome    python -c 'import datetime; print str(datetime.datetime.fromtimestamp(1458239719))'
> 2016-03-17 19:35:19
> $ TZ=UTC            python -c 'import datetime; print str(datetime.datetime.fromtimestamp(1458239719))'
> 2016-03-17 18:35:19
> 
> # utcfromtimestamp gives the same value regardless of TZ:
> $ TZ=America/Denver python -c 'import datetime; print str(datetime.datetime.utcfromtimestamp(1458239719))'
> 2016-03-17 18:35:19
> $ TZ=Europe/Rome    python -c 'import datetime; print str(datetime.datetime.utcfromtimestamp(1458239719))'
> 2016-03-17 18:35:19
> $ TZ=UTC            python -c 'import datetime; print str(datetime.datetime.utcfromtimestamp(1458239719))'
> 2016-03-17 18:35:19
> 

This is the problem, since you are setting the TZ to be Denver, Rome and then UTC, you would expect that
the output of the datetime call would differ, since when you cast it to string it should evaluate to the time
in the timezone of the caller.

You can better understand what I mean with this if you try to cast it to seconds since epoch again, as we
used to do in ooni-probe < 1.4:

$ TZ=America/Denver python -c 'import datetime; print datetime.datetime.utcfromtimestamp(1458239719).strftime("%s”)’
1458261319

$ TZ=Europe/Rome python -c 'import datetime; print datetime.datetime.utcfromtimestamp(1458239719).strftime("%s")’
1458236119

$ TZ=UTC python -c 'import datetime; print datetime.datetime.utcfromtimestamp(1458239719).strftime("%s")’
1458239719


~ Arturo