American time zones like CT, give error: ZoneInfoNotFoundError: 'No time zone found with key CT'

Python 3.9 introduced the zoneinfo module:

The zoneinfo module provides a concrete time zone implementation to support the IANA time zone database as originally specified in PEP 615. By default, zoneinfo uses the system’s time zone data if available; if no system time zone data is available, the library will fall back to using the first-party tzdata package available on PyPI.

On my Ubuntu machine, it supports lots of time zones:

>>> from zoneinfo import ZoneInfo
>>> ZoneInfo("America/New_York")
zoneinfo.ZoneInfo(key='America/New_York')
>>> ZoneInfo("MST") # Mountain Standard Time
zoneinfo.ZoneInfo(key='MST')
>>> ZoneInfo("CET") # Central European Time
zoneinfo.ZoneInfo(key='CET')

However, it doesn't seem to support some time zones abbreviations used in North America like Central Time (CT), Central Standard Time (CST) or Pacific Standard Time (PST).

>>> ZoneInfo("CT")
zoneinfo._common.ZoneInfoNotFoundError: 'No time zone found with key CT'
>>> ZoneInfo("CST")
zoneinfo._common.ZoneInfoNotFoundError: 'No time zone found with key CST'
>>> ZoneInfo("PST")
zoneinfo._common.ZoneInfoNotFoundError: 'No time zone found with key PST'

How can I get the right ZoneInfo objects for time zones like CT, CST or PST? Is the time zone database lacking? Does it depend on the operating system that I'm running?

There are issues with the abbreviations CT (Central Time), CST (Central Standard Time), PT (Pacific Time), and PST (Pacific Standard Time). Here are the main two:

• They do not identify a unique time zone. For example, CST could stand for Central Standard Time, but it could also stand for Cuban Standard Time or China Standard Time. The IANA database of time zones lists CST for all these areas.
• CST and PST are not appropriate during the summer, as most parts of the USA switch to daylight savings time during the period of the year that includes the summer. During the summer, the terms CDT (Central Daylight Time) and PDT (Pacific Daylight Time) should be used instead.

Central:

Instead of CT (CST during the winter or CDT during the summer), use US/Central or Canada/Central IANA identifier instead:

>>> from zoneinfo import ZoneInfo
>>> ZoneInfo("US/Central")
zoneinfo.ZoneInfo(key='US/Central')

Pacific:

Instead of PT (PST during the winter or PDT during the summer), use US/Pacific or Canada/Pacific instead:

>>> ZoneInfo("US/Pacific")
zoneinfo.ZoneInfo(key='US/Pacific')

Mountain:

For MT (MST during the winter and MDT during the summer), use US/Mountain for the areas that follow daylight savings time during the summer, and use America/Phoenix for the parts of Arizona that use MST all year round.

>>> ZoneInfo("US/Mountain")
zoneinfo.ZoneInfo(key='US/Mountain')
>>> ZoneInfo("America/Phoenix")
zoneinfo.ZoneInfo(key='America/Phoenix')

Note that Python does accept MST as a key. This identifier does not follow daylight savings time though, which you may not expect.

Eastern:

For ET (EST during the winter or EDT during the summer), use US/Eastern or Canada/Eastern:

>>> from zoneinfo import ZoneInfo
>>> ZoneInfo("US/Eastern")
zoneinfo.ZoneInfo(key='US/Eastern')

Note that Python does accept EST as a key. This identifier does not follow daylight savings time though, which you may not expect.

(Notice that parts of Arizona on the map represented by Phoenix don't observe Daylight Time)