IANA Time Zones for Central Time: A Reference Guide
Answer: There are 25 IANA time zones that fall under Central Time, with America/Chicago as the reference zone for US Central Time, plus zones across Mexico, Canada, and Central America that share the UTC-6 offset or the Central Time metazone.
25 Zones, One Metazone: Which IANA Identifiers Belong to Central Time
The IANA time zone database is the de facto technical standard for timekeeping worldwide. It is maintained by volunteers, used by all operating systems, programming languages, and network protocols. Each zone is a geographic region with a consistent history of local time, including offsets and daylight saving rules. For Central Time, the database records not just the UTC offset but the full DST transition history, which varies by country, state, and even city.
The CLDR metazone America_Central groups all 25 zones. That metazone is what operating systems and applications use to group zones with the same current offset and DST rules, even when the historical rules differ.
The Full List of 25 Central Time IANA Zones
The complete set: America/Bahia_Banderas, America/Belize, America/Chicago, America/Chihuahua, America/Costa_Rica, America/El_Salvador, America/Guatemala, America/Indiana/Knox, America/Indiana/Tell_City, America/Managua, America/Matamoros, America/Menominee, America/Merida, America/Mexico_City, America/Monterrey, America/North_Dakota/Beulah, America/North_Dakota/Center, America/North_Dakota/New_Salem, America/Ojinaga, America/Rankin_Inlet, America/Regina, America/Resolute, America/Swift_Current, America/Tegucigalpa, America/Winnipeg.
America/Chicago: The US Central Reference Zone
America/Chicago is the reference zone for US Central Time. It covers the largest population of any Central Time zone, including the city on Lake Michigan with 2,664,452 people, Houston (2,314,157), Dallas (1,326,087), and San Antonio (1,526,656). The zone observes Central Standard Time (CST, UTC-6) in winter and Central Daylight Time (CDT, UTC-5) in summer, following the US DST schedule from the second Sunday in March to the first Sunday in November.
When the Clocks Change in America/Chicago
In 2026, clocks go forward on Sunday 8 March at 02:00 local, moving 60 minutes to 03:00. CST (UTC-6) becomes CDT (UTC-5). Clocks go back on Sunday 1 November at 02:00 local, moving 60 minutes to 01:00. CDT (UTC-5) becomes CST (UTC-6).
In 2027, the spring change falls on Sunday 14 March and the autumn change on Sunday 7 November.
What the Offset Means for Cross-Zone Calls
On 15 January 2026, relative to America/Chicago on CST: New York is 1 hour ahead. Los Angeles is 2 hours behind. London is 6 hours ahead. Paris is 7 hours ahead. Dubai is 10 hours ahead. Mumbai is 11.5 hours ahead. Singapore is 14 hours ahead. Tokyo is 15 hours ahead. Sydney is 17 hours ahead. Johannesburg is 8 hours ahead. São Paulo is 3 hours ahead.
On 15 July 2026, relative to America/Chicago on CDT: New York is 1 hour ahead. Los Angeles is 2 hours behind. London is 6 hours ahead. Paris is 7 hours ahead. Dubai is 9 hours ahead. Mumbai is 10.5 hours ahead. Singapore is 13 hours ahead. Tokyo is 14 hours ahead. Sydney is 15 hours ahead. Johannesburg is 7 hours ahead. São Paulo is 2 hours ahead.
US Central IANA Zones: Split-State Variants and Why They Exist
The US has six additional IANA zones that fall under Central Time, mostly in split-state counties. These exist because of historical local decisions about DST observance.
| IANA Zone | Location | Notes |
|---|---|---|
| America/Chicago | Major US Central cities | Reference zone, US DST |
| America/Indiana/Knox | Knox County, Indiana | Central Time, follows US DST |
| America/Indiana/Tell_City | Tell City, Indiana | Central Time, follows US DST |
| America/Menominee | Menominee County, Michigan | Central Time, follows US DST |
| America/North_Dakota/Beulah | Beulah, North Dakota | Central Time, follows US DST |
| America/North_Dakota/Center | Center, North Dakota | Central Time, follows US DST |
| America/North_Dakota/New_Salem | New Salem, North Dakota | Central Time, follows US DST |
Why Indiana, Michigan and North Dakota Have Their Own Zones
These split-state variants exist because Indiana, Michigan, and North Dakota have counties that chose Central Time over Eastern or Mountain Time for geographic or economic reasons. The IANA database preserves these distinctions so that historical timestamps remain accurate.
Mexico Central IANA Zones: The Permanent Standard Time Split
Mexico has seven IANA zones that fall under Central Time. The country abolished DST nationally in October 2022, effective 2023, except for northern border municipalities that align with US DST for economic reasons. This creates a split: Mexico City is on CST year-round, while America/Chicago still springs forward and falls back.
| IANA Zone | Location | DST Status |
|---|---|---|
| America/Mexico_City | Mexico City and most of central/southern Mexico | No DST (permanent CST) |
| America/Matamoros | Matamoros, border with Brownsville, TX | US DST schedule |
| America/Ojinaga | Ojinaga, border with Presidio, TX | US DST schedule |
| America/Merida | Mérida, Yucatán | No DST |
| America/Monterrey | Monterrey, Nuevo León | No DST |
| America/Bahia_Banderas | Bahía de Banderas, Nayarit | No DST |
| America/Chihuahua | Chihuahua, Chihuahua | No DST |
The Scale of Mexico City on Central Time
Mexico City is the largest city in any Central Time zone, with a population of 12,294,193. Other major Mexican cities on Central Time include Iztapalapa (1,835,486), Puebla (1,692,181), Ecatepec de Morelos (1,645,352), Santiago de Querétaro (1,594,212), León de los Aldama (1,579,803), Zapopan (1,476,491), and Guadalajara (1,385,629).
Sunlight Across the Year in Mexico City
On the March equinox (20 March 2026): sunrise 06:41, sunset 18:47, 12 hours 6 minutes of sun. On the June solstice (21 June 2026): sunrise 05:58, sunset 19:16, 13 hours 18 minutes of sun. On the September equinox (22 September 2026): sunrise 06:24, sunset 18:33, 12 hours 9 minutes of sun. On the December solstice (21 December 2026): sunrise 07:05, sunset 18:03, 10 hours 57 minutes of sun.
Border Zones and the Cross-Border Business Reality
The border zones are critical for cross-border business. Matamoros and Brownsville, Texas share the same clock year-round. But Mexico City and the city on Lake Michigan are on the same time from November to March and diverge by one hour from March to November, when the US zone is on CDT and Mexico City remains on CST.
Canada Central IANA Zones: Saskatchewan's Year-Round CST
Canada has five IANA zones that fall under Central Time. Manitoba follows the US DST schedule, while Saskatchewan has a unique arrangement: it is geographically in the Mountain Time zone but legally observes CST year-round, effectively permanent daylight saving time.
| IANA Zone | Location | DST Status |
|---|---|---|
| America/Winnipeg | Manitoba | US DST schedule |
| America/Regina | Regina, Saskatchewan | No DST (permanent CST) |
| America/Swift_Current | Swift Current, Saskatchewan | No DST (permanent CST) |
| America/Rankin_Inlet | Rankin Inlet, Nunavut | US DST schedule |
| America/Resolute | Resolute, Nunavut | US DST schedule |
How Saskatchewan Compares to the US Reference Zone
Saskatchewan's choice means Regina matches America/Chicago in winter but is one hour behind in summer. Winnipeg, by contrast, matches America/Chicago year-round. The Nunavut zones follow US DST because of their northern location and economic ties to the south.
Central America IANA Zones: Six Countries on Year-Round CST
Six IANA zones in Central America fall under Central Time. All observe CST year-round with no DST, matching Mexico City's post-2022 schedule.
| IANA Zone | Country | DST Status |
|---|---|---|
| America/Belize | Belize | No DST |
| America/Costa_Rica | Costa Rica | No DST |
| America/El_Salvador | El Salvador | No DST |
| America/Guatemala | Guatemala | No DST |
| America/Managua | Nicaragua | No DST |
| America/Tegucigalpa | Honduras | No DST |
These zones are on UTC-6 year-round, meaning they match America/Chicago from November to March but are one hour behind from March to November.
How Developers Should Use Central Time IANA Zones
Never hardcode a UTC offset or DST rule. Use the IANA database through your operating system's zoneinfo or a library like Python's zoneinfo, Java's java.time, or JavaScript's Intl. Always store timestamps in UTC and convert to a user's IANA zone for display.
Why Does Mexico City Stay on CST While Chicago Moves to CDT?
The biggest trap in Central Time is the US-Mexico DST divergence. Most people assume Mexico follows US DST, but that ended in 2022. A meeting invitation that says "CST" in July is technically wrong for America/Chicago (which is on CDT) but correct for Mexico City (which is on CST year-round). Always specify the IANA zone or the exact UTC offset when scheduling across borders.
Saskatchewan's permanent CST confuses people who expect it to follow Mountain Time because of its geography. Regina matches America/Chicago in winter and is one hour behind in summer, which means it is effectively on permanent daylight saving time relative to its geographic position.
What Are the Different Meanings of "CST" in IANA Time Zones?
CST can mean Central Standard Time, China Standard Time (UTC+8), or Cuba Standard Time (UTC-5). CDT always means Central Daylight Time in North America. To avoid ambiguity, use "America/Chicago" or "UTC-6" in technical contexts, and say "Central Time" or "Central Daylight Time" in prose.
When Should You Use a Specific IANA Zone Instead of the Central Metazone?
The default advice to "use America/Chicago for Central Time" is wrong for anyone scheduling across the US-Mexico border. A logistics coordinator, a financial trader on the BMV or CME, or a software developer building scheduling tools should use the specific IANA zone for each location, not the metazone. The metazone groups zones that share current rules, but the border zones (America/Matamoros, America/Ojinaga) have different DST behavior from the interior zones (America/Mexico_City, America/Monterrey). The correct approach is to resolve each city to its precise IANA zone and let the database handle the rest.