How to read a tz database zone name
Every zone in the tz database has a name of two or three parts: an area such as Europe or America, sometimes a subregion, and a reference city, as in Europe/Paris or America/Argentina/Buenos_Aires. The main table holds 312 such names, and 237 further names point to them.
Area and city
The first part of a name is a continent or ocean. America covers both North and South America, and the ocean areas, Atlantic, Indian and Pacific, hold islands. The table shows how the 312 zones are spread.
| Area | Zones |
|---|---|
| America | 121 |
| Asia | 74 |
| Europe | 38 |
| Pacific | 30 |
| Africa | 19 |
| Australia | 11 |
| Antarctica | 8 |
| Atlantic | 8 |
| Indian | 3 |
The second part is a city. The project’s guidelines (the theory file in each release) ask for the most populous city of the zone, not necessarily the capital, which is why China’s zone is Asia/Shanghai. Spaces become underscores, so the zone for New York is written America/New_York. The city is a label for the whole region whose clocks have agreed since 1970, which is why the site shows each zone with the area it covers as well as the city.
Three-part names
25 names have a middle part for a subregion: Argentina (12), Indiana (8), North_Dakota (3) and Kentucky (2). These group places within one country or state whose clock histories differ. The eight zones for Indiana, for example, keep apart counties whose clocks disagreed at various times; the last change of standard time among them was in 2007.
One record, several countries
A zone can cover more than one country. When places have kept the same clocks since 1970, the database keeps a single record and lists the others as alternative names for it. Puerto Rico is the extreme case: its record is used in 20 countries and territories across the Caribbean. Côte d’Ivoire follows with 12 in West Africa, including Ghana and Iceland. The five zones used by the most countries are Puerto Rico (20), Côte d’Ivoire (12), Nigeria (10), Kenya (10) and Mozambique (8).
The same rule decides which countries have a page of their own on this site. 154 countries and territories have at least one zone of their own; 25 of them have several. Another 93 follow a neighbour’s record and are listed on the country index with the record they follow. Two territories, Bouvet Island and Heard Island and McDonald Islands, have no zone at all.
Older names
The alternative names include older forms that are kept so that software written years ago still works. Some are country or region names such as Japan or GB; others belong to a United States scheme that predates the current names, such as US/Eastern for America/New_York. The site lists them on each zone page under “other names for this record”. There are 43 names of this kind among the 237 alternatives.
Countries with the most zones
Large countries are split into several zones when their regions have kept different clocks since 1970. In the database United States has 29, Russia 26, Canada 20, Brazil 16, Argentina 12 and Australia 12 zones of their own. These splits follow history, not size alone: China, one of the largest countries, has 2, and India has 1.
Renamed cities
When a city’s English spelling changes, the database adopts the new name and keeps the old one as an alternative, so both still work. Examples in the current release include Asia/Kolkata for the older Asia/Calcutta, Europe/Kyiv for the older Europe/Kiev, Asia/Ho_Chi_Minh for the older Asia/Saigon, America/Nuuk for the older America/Godthab and Asia/Yangon for the older Asia/Rangoon. On this site the current name is used everywhere, and the old ones are listed on the zone page. Software that stores a zone name, such as a calendar entry, can therefore keep working after a rename, because the old name points to the same record.
Abbreviations
Abbreviations such as EST or CET are not part of the zone name, and the database does not invent them. Where no abbreviation is in common English use, it writes the offset instead, such as +04. Under the current rules, 148 of the 312 zones have no alphabetic abbreviation at all. This is why the converter shows the full offset next to any abbreviation.
Using names on this site
Each zone page gives its database name, its alternative names and the countries that use it. The zone index lists all 312 names, and the search box on the home page accepts country names, city names and database names.
Source: IANA Time Zone Database, release 2026f (public domain), computed by this site; see about the data for definitions. Look up any zone in the converter.