-- Assume my session time zone is 'America/New_York' SET TIME ZONE 'America/New_York'; -- Create a test table CREATE TABLE time_test ( ts_native TIMESTAMP, -- without tz ts_tz TIMESTAMPTZ -- with tz );
CREATE TABLE events ( id SERIAL, local_start TIMESTAMPTZ, -- absolute moment in UTC user_time_zone TEXT -- 'America/Los_Angeles' ); | Feature | TIMESTAMP | TIMESTAMPTZ | |---------|-------------|----------------| | Time zone awareness | ❌ No | ✅ Yes (UTC internally) | | Changes with client time zone | ❌ No | ✅ Yes (on output) | | Safe for global apps | ❌ Risky | ✅ Safe | | Storage size | 8 bytes | 8 bytes (same!) |
# Django/ORM example from django.utils import timezone import datetime bad_time = datetime.datetime(2025, 4, 14, 14, 0, 0) GOOD: Aware datetime good_time = timezone.now() # includes UTC offset postgres timestamp vs timestamptz
If you have ever built an app that serves users across multiple time zones, you’ve likely woken up to a 3:00 AM page about "incorrect order dates" or "meetings showing up at the wrong hour."
Now, what is stored?
If your column is TIMESTAMPTZ , but your application sends a naive timestamp, PostgreSQL will assume the timestamp is in your session's time zone. If your server is in UTC and your user is in Sydney – .
If you change your session time zone to 'Asia/Tokyo' (UTC+9) and read the table: -- Assume my session time zone is 'America/New_York'
Chances are, you chose the wrong PostgreSQL temporal data type.