'Converting dates from past to UTC time

I'm trying to convert Bill Clinton's Birthday

August 19, 8:51 AM - Hope, Arkansas

To UTC Time but I keep getting discrepancies.

In python when I do

import datetime 
from datetime import timezone
from zoneinfo import ZoneInfo
dt = datetime(1946, 8, 16, 8, 51, tzinfo=ZoneInfo('America/Chicago'))

dt.astimezone(timezone.utc) 
# This returns 
#datetime.datetime(1946, 8, 16, 13, 51, tzinfo=datetime.timezone.utc)

All libraries I use and even online date to UTC time converters converts the date to 13:51 UTC.

However, official astrology datasets such as https://www.astro-seek.com/birth-chart/bill-clinton-horoscope, https://www.astro.com/astro-databank/Clinton,_Bill, etc

All compute his natal chart (not important to understand what it is if you don't know astrology) using his birth time as 14:51 UTC, even though they all still use the proper local time.

My question is: What is causing this discrepancy and how do I know which UTC time is right?



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