# How many US time zones are there?

Lists the time zones of the US with the local time, abbreviation, UTC offset, and daylight saving in each, for any time and date.

- Page: https://www.acalculator.org/days/us-time-zones
- JSON spec: https://www.acalculator.org/days/us-time-zones.json
- Version: 00795d74081f

## Default answer

Example with the default inputs (Time 12:00, In Eastern: New York, Date September 30, 2026) on the example date Wednesday, September 30, 2026: At 12:00 PM on September 30, 2026 in Eastern: New York, the US has 6 time zones and 7 UTC offsets in use.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| at | Time | A clock time in the zone chosen below; the table shows that moment in every zone. |
| zone | In | The time zone of the time above (IANA name). |
| on | Date | The date of that time in that zone. Today, unless you change it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| zones | Time zones | The number of different standard UTC offsets among the zones listed for the US. |
| inUse | UTC offsets in use at that moment | The number of different UTC offsets the listed zones show at that moment, daylight saving included. |
| new_york | Eastern: New York | Local time, abbreviation, UTC offset, and daylight saving in America/New_York at that moment. |
| chicago | Central: Chicago | Local time, abbreviation, UTC offset, and daylight saving in America/Chicago at that moment. |
| denver | Mountain: Denver | Local time, abbreviation, UTC offset, and daylight saving in America/Denver at that moment. |
| phoenix | Mountain, no DST: Phoenix, Arizona | Local time, abbreviation, UTC offset, and daylight saving in America/Phoenix at that moment. |
| los_angeles | Pacific: Los Angeles | Local time, abbreviation, UTC offset, and daylight saving in America/Los_Angeles at that moment. |
| anchorage | Alaska: Anchorage | Local time, abbreviation, UTC offset, and daylight saving in America/Anchorage at that moment. |
| adak | Hawaii-Aleutian: Adak, Alaska | Local time, abbreviation, UTC offset, and daylight saving in America/Adak at that moment. |
| honolulu | Hawaii-Aleutian, no DST: Honolulu | Local time, abbreviation, UTC offset, and daylight saving in Pacific/Honolulu at that moment. |

## Method

For the typed time in the chosen zone, find the instant (UTC) it names, then show each listed zone’s clock at that instant with its UTC offset, from the browser’s IANA time zone data.

## Assumptions

- The zones are IANA tzdata names from zone1970.tab (tzdata 2026a): America/New_York, America/Chicago, America/Denver, America/Phoenix, America/Los_Angeles, America/Anchorage, America/Adak, Pacific/Honolulu. The browser supplies each zone's offsets and daylight saving rules, so a rule change arrives with a browser update.
- “Time zones” counts the different standard offsets among the listed zones. A zone’s standard offset in a year is the lower of its offsets at 00:00 UTC on January 1 and July 1 of that UTC year.
- “UTC offsets in use” counts the different offsets the listed zones show at that moment.
- Each zone shows its local time, the abbreviation from the browser’s Unicode CLDR English names (left out when CLDR has none), the date as “Tue, Sep 29”, the offset as UTC+hh:mm or UTC−hh:mm, and “daylight saving” when the offset is ahead of the standard offset, “standard time” when the zone’s January 1 and July 1 offsets differ but it is on the standard offset, or “no daylight saving” when they are the same. Because the rule compares January 1 and July 1, a zone that moves its offset for good during a year (Cancún in 2015, Novosibirsk in 2016), or whose January 1 falls in Morocco’s Ramadan change (Casablanca in 2030 to 2033), shows the later offset as “daylight saving” for that year.
- A time that does not exist in the chosen zone (skipped when clocks spring forward) has no answer. A time that occurs twice (when clocks fall back) shows both moments, earlier first, where they differ.
- Dates from 2000 to 2040 work.

## Worked examples

1. at = 12:00, zone = America/New_York, on = 2026-01-15 gives zones = 6, inUse = 6, new_york = 12:00 PM EST · Thu, Jan 15 · UTC−05:00 · standard time, chicago = 11:00 AM CST · Thu, Jan 15 · UTC−06:00 · standard time, denver = 10:00 AM MST · Thu, Jan 15 · UTC−07:00 · standard time, phoenix = 10:00 AM MST · Thu, Jan 15 · UTC−07:00 · no daylight saving, los_angeles = 9:00 AM PST · Thu, Jan 15 · UTC−08:00 · standard time, anchorage = 8:00 AM AKST · Thu, Jan 15 · UTC−09:00 · standard time, adak = 7:00 AM HAST · Thu, Jan 15 · UTC−10:00 · standard time, honolulu = 7:00 AM HST · Thu, Jan 15 · UTC−10:00 · no daylight saving. Source: IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones).
2. at = 12:00, zone = America/New_York, on = 2026-07-15 gives zones = 6, inUse = 7, new_york = 12:00 PM EDT · Wed, Jul 15 · UTC−04:00 · daylight saving, chicago = 11:00 AM CDT · Wed, Jul 15 · UTC−05:00 · daylight saving, denver = 10:00 AM MDT · Wed, Jul 15 · UTC−06:00 · daylight saving, phoenix = 9:00 AM MST · Wed, Jul 15 · UTC−07:00 · no daylight saving, los_angeles = 9:00 AM PDT · Wed, Jul 15 · UTC−07:00 · daylight saving, anchorage = 8:00 AM AKDT · Wed, Jul 15 · UTC−08:00 · daylight saving, adak = 7:00 AM HADT · Wed, Jul 15 · UTC−09:00 · daylight saving, honolulu = 6:00 AM HST · Wed, Jul 15 · UTC−10:00 · no daylight saving. Source: IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones).

## FAQ

### How many time zones does the US have?

The 50 states use 6 standard time zones: Eastern (UTC−05:00), Central (UTC−06:00), Mountain (UTC−07:00), Pacific (UTC−08:00), Alaska (UTC−09:00), and Hawaii-Aleutian (UTC−10:00). US law sets nine zones in all: it adds Atlantic (Puerto Rico and the US Virgin Islands), Samoa, and Chamorro (Guam and the Northern Mariana Islands).

### Which states are in two time zones?

Florida, Idaho, Indiana, Kansas, Kentucky, Michigan, Nebraska, Nevada, North Dakota, Oregon, South Dakota, Tennessee, and Texas each have counties in two of the zones. Alaska has two as well: Alaska time, and Hawaii-Aleutian time in the Aleutian Islands west of 169°30′ W.

### Do Arizona and Hawaii use daylight saving time?

No. Hawaii and most of Arizona keep standard time all year, as federal law allows a state to do; the Navajo Nation in northeastern Arizona does change its clocks. So from March to November Arizona shows the same time as California, and in winter the same time as Denver.

### When do US clocks change?

Daylight saving time starts at 2:00 AM local time on the second Sunday in March and ends at 2:00 AM local time on the first Sunday in November. In 2026: Sunday, March 8, 2026 and Sunday, November 1, 2026. Each zone changes at its own 2:00 AM, so for an hour two neighbouring zones are 2 hours apart in March and show the same time in November.

## Sources

- 15 U.S.C. 263, standard time zones (https://www.law.cornell.edu/uscode/text/15/263)
- 15 U.S.C. 260a, advancement of time (https://www.law.cornell.edu/uscode/text/15/260a)
- 49 CFR part 71, standard time zone boundaries (https://www.ecfr.gov/current/title-49/subtitle-A/part-71)
- IANA Time Zone Database, tzdata 2026a (https://www.iana.org/time-zones)