log_timezone

log_timezone is the PostgreSQL setting that defines the time zone to use in log messages.

Note

Fact — official short description: “Sets the time zone to use in log messages.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuesighup: Takes effect after configuration reload
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueReporting and Logging / What to Log: Upstream classification
Latest boot value , ValueGMT: GMT

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

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.0	`UNKNOWN`	—	UNKNOWN
PG9.1	—	—	not set
PG9.2–19 Beta 3	`GMT`	—	GMT

How it works

log_timezone sets the time zone to use in log messages. It affects timestamps rendered by the logging system, including filename expansion context, but does not change session TimeZone or stored timestamps.

log_timezone is a SIGHUP-context setting: a configuration reload activates the new server value without a restart; subsequent operations that consult it use the refreshed value.

It changes emitted diagnostic data rather than query semantics, but volume, sensitive content, log_line_prefix, destinations, collector throughput, and retention determine operational cost and usefulness.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Use one cluster-wide timezone, normally UTC, so every session’s server-log timestamps correlate across hosts, replicas, failovers, and centralized ingestion. Test parsers and log_filename expansion before changing it.
OLAP	Analytical workload type does not justify a separate log timezone. Keep UTC or the fleet standard and convert to local civil time only in reporting tools, especially across DST transitions.
Small nodes	Keep UTC unless an existing operational pipeline requires another stable zone. Changing log_timezone does not reduce log volume; it changes timestamp interpretation and potentially rotated filenames.

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	`UTC`	different	`'UTC'`
OLAP	`UTC`	different	`'UTC'`
CRIT	`UTC`	different	`'UTC'`
TINY	`UTC`	different	`'UTC'`

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = UTC (dcs); OLAP: PG9.0–19 Beta 3 = UTC (dcs); CRIT: PG9.0–19 Beta 3 = UTC (dcs); TINY: PG9.0–19 Beta 3 = UTC (dcs). Advice, pending human review — Editorial inference: UTC makes timestamps comparable across hosts, regions, failovers, and centralized log systems.

Common pitfalls

Editing log_timezone without reloading configuration and verifying the effective value and subsequent behavior.
Enabling richer logging without budgeting collector throughput, storage, retention, and downstream query cost.
Writing SQL text, bind values, identities, or host data without a redaction and access-control policy.
Changing log_timezone globally without a rollback plan and a client or operational compatibility test.

DateStyle · IntervalStyle · TimeZone · lc_time · timezone_abbreviations