Working with time zone information

Time Series Analysis in PostgreSQL

Jasmin Ludolf

Content Developer, DataCamp

Time zone data

TIMESTAMP : date and time information without time zone
- Fine when using a single time zone
- All times are in UTC
TIMESTAMPTZ : date and time with time zones

Illustration of four clock faces with different times.

Time zone names

SELECT * FROM pg_timezone_names;

| name             |abbrev|utc_offset|is_dst|
|------------------|------|----------|------|
|Africa/Abidjan    |GMT   |  00:00:00|false |
|Africa/Accra      |GMT   |  00:00:00|false |
|Africa/Addis_Ababa|EAT   |   3:00:00|false |
...

is_dst : whether the location is observing daylight savings

Show the time zone

SHOW TIMEZONE;

|TimeZone       |
|---------------|
|Europe/Brussels|

Time zone data in tables

datetimes table has the following two fields:
- datetime : TIMESTAMP
- datetimetz : TIMESTAMPTZ

INSERT INTO datetimes (datetime, datetimetz)
VALUES('2023-01-03 12:00:00','2023-01-03 12:00:00');

|datetime           |datetimetz               |
|-------------------|-------------------------|
|2023-01-03 12:00:00|2023-01-03 12:00:00+01:00|

Verify the data type

pg_typeof(field_name): check the data type of the field

SELECT
    pg_typeof(datetime) AS "type of(datetime)", 
    pg_typeof(datetimetz) AS "type of(datetimetz)"
FROM datetimes;

|type of(datetime)          |type of(datetimetz)     |
|---------------------------|------------------------|
|timestamp without time zone|timestamp with time zone|

Using time zone information

INSERT INTO datetimes (datetime, datetimetz)
VALUES('2023-01-03 12:00:00+00','2023-01-03 12:00:00+00');

SELECT * FROM datetimes;

|datetime           |datetimetz               |
|-------------------|-------------------------|
|2023-01-03 12:00:00|2023-01-03 12:00:00+01:00|
|2023-01-03 12:00:00|2023-01-03 13:00:00+01:00|

Adding time zone information

AT TIME ZONE: Add, change, or remove time zone information
- Converting the type from TIMESTAMP to TIMESTAMPTZ and vice versa

Adding a time zone:

SELECT 
    TIMESTAMP '2020-12-31 23:59:59' AT TIME ZONE 'Europe/London' AS added;

|added                    |
|-------------------------|
|2021-01-01 00:59:59+01:00|

This query: interprets the timestamp, creates TIMESTAMPTZ, displays the default

Changing and removing time zones

SELECT 
    '2020-12-31 23:59:59+00'::TIMESTAMPTZ AT TIME ZONE 'Europe/Paris' 
    AS shifted;

|shifted            |
|-------------------|
|2021-01-01 00:59:59|

This query: shifts the timestamp to the desired time zone, removes the time zone designation

Let's practice!

Time Series Analysis in PostgreSQL