It is critically important for an astrologer to know the exact time of a person's birth. It also includes understanding the actual time zone in the selected city at the time of birth.
Due to many state orders and decrees, the transition to daylight saving time was irregular. Not all computer applications consider all known time corrections for the selected city at a given time.
We decided to fix it and created a simple visualizer for the most accurate daylight saving time database from the Internet Assigned Numbers Authority (IANA).
Just select the desired city and century, and see how the time zone in this city has changed over the years. It will help you to set the correct GMT offset and cast a birth chart without errors.