IATA codes are abbreviations that the International Air Transport Association (IATA) publishes to facilitate air travel. They are typically 1, 2, 3, or 4 character combinations (referred to as unigrams, digrams, trigrams, or tetragrams, respectively) that uniquely identify locations, equipment, companies, and times to standardize international flight operations. All codes within each group follow a pattern (same number of characters, and using either all letters or letter/digit combinations) to reduce the potential for error.
IATA timezone is a country or a part of a country, where local time is the same. IATA timezone code is constructed of 2-4 characters (letters an digits) as follows:
ISO 3166-1 alpha-2 country code is always used as first and second characters of time zone code.
If country is not divided into separate time zones - no more characters added. Just 2 characters used.
If country is divided into time zones - 3rd character of time zone code is a digit - number of time zone in country. Note:Russia is divided into 11 timezones, so number of time zone in country is specified by 2 digits - RU01, RU02, ... RU11.
If some territories have the same local time, but different rules on Daylight saving time, - a letter can be added as 4th character to make unique codes for all such territories.
Example: Time zone code AU2 is used for Australian states New South Wales and Victoria (local time is UTC + 10 hours, DST begins at end of October). Time zone code AU2A is used for Tasmania (local time is UTC + 10 hours, DST begins at end of September). Time zone code AU2B is used for Queensland (local time is UTC + 10 hours, no DST).
IATA region codes
IATA region codestrigram letters codes used to specify large territories, consisting of several countries.
Speaking on region codes and countries, country code RU is used to specify part of Russia west from (and including of) Ural Mountains and country code XU is used to specify part of Russia east from (and not including of) Ural Mountains. Country RU is in EUR region, country XU is in SEA region. For all other purposes only country code RU is used to specify all the territory of Russia.
Country code AQ is used to specify Antarctica. Country AQ is not in any of regions listed here.