Subject: pg_timezone_names

From: PG Doc comments form <[email-masked]>
Date: Wed, 17 Jan 2018 17:16:41 +0000

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.1/static/view-pg-timezone-names.html
Description:

We are exporting data from postgres into another "all in one" data store,
and i had a quick question regarding the time offsets.  The UTC_OFFSET, does
it change when IS_DST is true/false?  Or do I need to take the UTC_OFFSET
interval and then possibly add 1 more if IS_DST is true?  Example: 1/1/2018
not in DST, interval says -10.  On 3/1/2018, IS_DST turns to TRUE.  Will the
interval now say -9, or do i need to take the -10 and substract 1 to get to
-9?

---

From: Tom Lane <[email-masked]>
Date: Wed, 17 Jan 2018 12:33:29 -0500

=?utf-8?q?PG_Doc_comments_form?= <[email-masked]> writes:
> it change when IS_DST is true/false?

Yes; utc_offset reflects the zone's current offset from UTC, so it changes
with the seasons if the zone has DST laws.

> Or do I need to take the UTC_OFFSET
> interval and then possibly add 1 more if IS_DST is true?

Prepare to be disappointed; you can't assume it works like that.
See the thread starting here:

http://mm.icann.org/pipermail/tz/2017-December/025682.html

You haven't said what it is you are hoping to accomplish, so it's
hard to say if there's some safer way to do it.

			regards, tom lane