Olson DB: which version in PostgreSQL?

Question

I have an application heavily relying upon timezones, and I am using PostgreSQL for storing and querying my data. I'm letting the user choosing their own timezone, by showing the list of postgresql's supported timezones, in their extensive form (i.e. Europe/Rome). All the information concerning time/date are crunched by PostgreSQL itself, whereas my scripting language (PHP) simply fetches data and serves it without altering time-based data.

When the user wants to modify her/his own timezone, I return the timezone list by using a query like this:

SELECT tz.name AS measure, tz.utc_offset AS utc_offset, tz.is_dst AS is_dst FROM pg_timezone_names() tz;

Users will be able to choose their timezone by specifying the extended timezone name tz.name. I'm not using nor allowing any timezone abbreviation in any way.

According to the official docucmentation I can change the timezone abbrevs, but I'm not finding any piece of information about the Olson DB's version used by Postgres. I really would like to have control on the Olson DB, so:

1. Where can I find any information about the timezone's DB version used?
2. Is it possible updating the timezone's DB by replacing the newest official IANA version? Consider a legacy system with Postgres 8.4 and no chance of updating it.

Thanks so much guys

• joanolo: AFAIK, timezones and how they work is managed by PostgreSQL itself. We, users, aren't supposed to modify the system tables "by hand". My guess (based on the existence of folders timezone and timezonesets within the PostgreSQL folder) is that some part of this information [specially regarding DST rules] is so sophisticated it cannot be handled by just a list on a table.
• Evan Carroll: What version of the database are you using?

Answer 1

Currently (Jan 23, 2017)

• PostgreSQL uses IANA (Olson) version 2016j
• 2016j is the latest version.
• tz-updates are rolled out to supported major versions in point releases. 9.2 is still supported (current as of Jan 2017) with TZ upgrades.

You can see the change long for the tz database upstream here

1. Where can I find any information about the timezone's DB version used?

check out the README in src/timezone/README which says "the code in this directory is currently synced with tzcode release 2016j."

2. Is it possible updating the timezone's DB by replacing the newest official IANA version? Consider a legacy system with Postgres 8.4 and no chance of updating it.

It's already the latest version, but I imagine if it ever falls behind patches would be accepted. You can find the instructions to create the patch in the README file above.