# timezone_abbreviations

> timezone_abbreviations is the PostgreSQL setting that selects a file of time zone abbreviations.
---

> [!NOTE]
> **Fact — official short description:** “Selects a file of time zone abbreviations.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `string` | Upstream pg_settings type |
| Context | `user` | Settable by an ordinary user |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Client Connection Defaults / Locale and Formatting | Upstream classification |
| Latest boot value | — | not set |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–19 Beta 3 |
| Removed in | No |
| Introduction commit | Not asserted: predates the PG9.0 research boundary |
| Commit date | — |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0 | `UNKNOWN` | — | UNKNOWN |
| PG9.1–19 Beta 3 | — | — | not set |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

timezone_abbreviations selects a file of time zone abbreviations. The selected set changes accepted datetime input tokens and can make the same abbreviation resolve differently by region.

timezone_abbreviations is a USER-context setting. An authorized role can change it for a session, while ALTER ROLE or ALTER DATABASE can establish a default for future sessions.

It changes representation, parsing, or locale behavior at the client boundary rather than physical storage. Coordinate it with the other locale and formatting settings and with driver-native binary or typed protocols.

## Tuning advice {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Treat timezone_abbreviations as an application contract, not a performance knob. Standardize it per role or connection pool and keep wire formats explicit where clients parse text. |
| OLAP | Pin timezone_abbreviations for export, reporting, and reproducible analytical jobs; prefer explicit SQL formatting when a file or API has a durable schema. |
| Small nodes | Keep the upstream or locale-derived value unless a client requires another one. A smaller server gains no capacity from changing timezone_abbreviations. |
{.full-width}

## Pigsty {#pigsty}

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

| Template | Effective value | Versus upstream boot | Source expression |
| --- | --- | --- | --- |
| OLTP | Unmodified | — | — |
| OLAP | Unmodified | — | — |
| CRIT | Unmodified | — | — |
| TINY | Unmodified | — | — |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Changing timezone_abbreviations in one session and assuming role defaults, database defaults, or other pooled sessions changed with it.
- Assuming a presentation setting changes stored values or server-side type semantics.
- Changing a role or database default without testing text-parsing clients, exports, and pooled sessions.
- Accepting a region-specific abbreviation set that gives familiar tokens a different UTC offset.

## Related parameters {#related-parameters}

[`DateStyle`](/parameters/datestyle/) · [`IntervalStyle`](/parameters/intervalstyle/) · [`TimeZone`](/parameters/timezone/) · [`lc_time`](/parameters/lc-time/) · [`log_timezone`](/parameters/log-timezone/)

## References {#references}

- [PostgreSQL 19 Beta 3 — timezone_abbreviations](https://www.postgresql.org/docs/19/runtime-config-client.html#GUC-TIMEZONE-ABBREVIATIONS)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)