Re: Content for talk on Postgres Type System at PostgresConf

[Guyren Howe <guyren@xxxxxxxxx>]

On 29 Feb 2024, at 14:51, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:

- time with time zone *does* store the time zone, but this isn’t
actually useful and should be avoided (I’m not entirely sure why and the
docs only gesture at the problems without stating them, IIRC)

No it doesn't store the time zone.  Nor do the docs say they do.  And
clearly point out the issue that evaluating a time zone without both date
and time inputs is basically pointless.

timetz *does* store a time zone, in the sense of storing a numeric
offset from UTC (i.e., "so many minutes east or west of Greenwich").
The problem is that in most real-world applications your notion of
"time zone" probably includes annual DST changes, which timetz can't
represent.  I don't say the type is completely useless, but its
usefulness is a lot less than you might guess.

The closest I can come to this in the docs is:

"The appropriate time zone offset is recorded in the time with time zone value and is output as stored; it is not adjusted to the active time zone.”

I expect to be submitting some documentation updates as part of this project, fwiw.