That is my understanding as well, a timestamp either has a timezone or it has not. If it does not have a timezone, it should be presented as is and no assumptions can be made about its timezone. In particular, but given two fields X and Y, one with a timezone and another without, e.g. it is not meaningful to compute X - Y.
Maybe a way of framing: given an uint64 X in parquet with "isAdjustedToUTC=true", which arrow's datatype and value Y should it correspond to? A timestamp with or without a timezone? I have so far understood that "isAdjustedToUTC=false" corresponds to no timezone in arrow, and "isAdjustedToUTC=true" corresponds to "+00:00". (But maybe this is incorrect?) Best, Jorge On Thu, Jun 3, 2021 at 6:59 PM Julian Hyde <jhyde.apa...@gmail.com> wrote: > My answer to Antoine’s question would not be “kind of”, it would be “no”. > > In a system such as Joda-time, which I claim is the only system that Arrow > should be considering, a timestamp-without-timezone does not have an > implicit time zone of UTC. It has no time zone. > > > > On Jun 3, 2021, at 8:52 AM, Micah Kornfield <emkornfi...@gmail.com> > wrote: > > > >> > >> Aren't those exactly the same (i.e. no timezone implicitly means UTC, > >> not local time)? > > > > > > Kind of, the reason we went with this approach is this sentence from the > > specification: > > > > "the data is "time zone naive" and shall be displayed *as is* to the > user, > > not localized to the locale of the user.", which seemed like the closest > > match for what Date times actually does. Computationally this isn't > really > > ideal. > > > > -Micah > > > > On Thu, Jun 3, 2021 at 12:32 AM Antoine Pitrou <anto...@python.org> > wrote: > > > >> > >> Le 02/06/2021 à 22:56, Micah Kornfield a écrit : > >>>> > >>>> Any SQL interface to Arrow should follow the SQL standard. So, for > >>>> instance, if a column has TIMESTAMP type, it should behave as a > >>>> date-time without a time-zone. > >>> > >>> > >>> At least in bigquery we do the following mapping: > >>> SQL TIMESTAMP -> Arrow Timestamp with "UTC" timezone > >>> SQL DATETIME -> Arrow Timestamp without a time-zone. > >> > >> Aren't those exactly the same (i.e. no timezone implicitly means UTC, > >> not local time)? > >> > >> Regards > >> > >> Antoine. > >> > >
