I'm trying to create HTTP endpoints:

1. one that returns posts to a user that were created in a given month in the requestor's time zone.
2. another one that gets the months possible for post*.

Examples

(1) get posts in month of requestor's timezone

(2) get possible months for posts

For example if the user made posts in Sept-November but none in December then Jan onward it wouldn't return December. But it takes the time zone in "PST" format, because it does a SQL query.

Problems

Unfortunately pytz, the library I'm using for getting all posts from a month, only accepts time zone in the format "US/Pacific".

Questions

1. What is the format or string representation "US/Pacific" called ?
2. How can I convert the string formats "PST", "UCT" or "CST" to their respective formats like "US/Pacific", etc. in Python ?
3. What's the name for this format like "US/Pacific" ?
4. Is there a sort of dictionary that maps "PST" to "US/Pacific" ?

5

2 Answers

Time zone terminology

How to define, represent or refer to a time zone? Some terms:

• UTC time offset (e.g. "UTC-08:00")
• in relation with ISO 8601 date/time format: time zone designator (e.g. "Z" or "-08")
• time zone: canonical name
• time zone: abbreviation

(Canonical) names

The spelled-out time zone names or (tz names) like "US/Pacific" or "Europe/Paris" are also called canonical names of time zone. They are used as key in the IANA time zone database. In RFC 6557 they are referred to as "time zone names". Wikipedia claims about them:

The primary, preferred zone name.

See also:

• ECMA: 6.4Time Zone Names

Abbreviations

The alphabetic string literals like "UTC", "PST" are abbreviations of time zone.

Conversion between time zones

Usually the conversion between time zones is done by modifying the offsets of UTC which are represented in ISO 8601, time zone designators like "-0800" (PST) which is 8 hours subtracted from "+0000" (UTC).

See also:

• Daylight saving time and time zone best practices

Converting using pytz timezone

To convert a given date-time from UTC to the target time zone (e.g. "US/Pacific") use astimezone(tz) on the source date-time instance:

import datetime
from pytz import timezone, utc
utc_time = datetime.datetime.utcnow()
pst_tz = timezone('US/Pacific')
pst_time = utc_time.replace(tzinfo=utc).astimezone(pst_tz)

Note:

• the time-zone tz is built using pytz's tzinfo API, e.g. with timezone('PST8PDT') for PST or timezone('US/Central') for CST
• the .replace() is optional and resets the time zone of given date-time to default UTC.

Surprisingly: The "PST" abbreviation is not found in pytz.all_timezones. Most similar are (evaluated in REPL):

>>> import pytz
>>> pytz.timezone('PST8PDT')
<DstTzInfo 'PST8PDT' PST-1 day, 16:00:00 STD>
>>> pytz.timezone('US/Pacific')
<DstTzInfo 'US/Pacific' LMT-1 day, 16:07:00 STD>
>>> pytz.timezone('US/Central')
<DstTzInfo 'US/Central' LMT-1 day, 18:09:00 STD>

See also:

• pytz - Converting UTC and timezone to local time
• Is there a list of Pytz Timezones?

Converting using zoneinfo (since 3.9)

Adjusted from MrFuppes answer to "How do I use timezones with a datetime object in python?":

from datetime import datetime, timezone
from zoneinfo import ZoneInfo
utc_time = datetime(2012,11,10,9,0,0, tzinfo=timezone.utc)
cst_tz = ZoneInfo("US/Central")
cst_time = utc_time.astimezone(cst_tz)
# safely use `replace` to get the same wall time in a different tz:
pst_time = cst_time.replace(tzinfo=ZoneInfo("US/Pacific"))
print(utc_time.isoformat())
print(cst_time.isoformat())
print(pst_time.isoformat())

(above code is not tested!)

See also:

• new Python module zoneinfo — IANA time zone support
• Paul Ganssle (2021): Stop using utcnow and utcfromtimestamp, blog article from the maintainer of python-dateutil

4

import pytz
from datetime import datetime # timezone
print('The supported tz:', pytz.all_timezones, '\n')
# Show date-time for different timezone/country
# current date and time of NY
datetime_NY = datetime.now(pytz.timezone('America/New_York'))
print("NY:", datetime_NY.strftime("%m/%d/%Y, %H:%M:%S"))
# NY: 07/28/2021, 05:49:41
# Timezone Conversion
# Any timezone to UTC
NY_to_utc = datetime_NY.astimezone(pytz.utc)
print("NY_to_utc: ", NY_to_utc.strftime("%m/%d/%Y, %H:%M:%S"))
# NY_to_utc: 07/28/2021, 09:49:41

Naive and Aware datetime Refer this article for dealing with timezone

1. Show date-time for different timezone/country
2. Timezone Conversion
3. Timezone unaware/naive to Timezone aware
4. Issue with replace

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy