ZIP Codes by Time Zone: Eastern, Central, Mountain & Pacific
If you need to know which ZIP codes belong to Eastern, Central, Mountain, or Pacific Time, this guide brings the four major contiguous-U.S. time zones into one reference. It combines a readable state-level overview with ZIP examples and a direct lookup workflow so you can move from a broad question such as “what ZIP codes are in Mountain Time?” to an exact five-digit ZIP answer.
Quick Answer
The contiguous United States has four primary standard time zones: Eastern, Central, Mountain, and Pacific. The U.S. Department of Transportation oversees U.S. time zones and the federal regulatory framework for their boundaries. NIST documents the standard and daylight designations used for each zone.
The most important rule for ZIP searches is simple: do not infer a ZIP's time zone only from its state. Some states cross time-zone boundaries. A ZIP-level lookup is more precise than a state-level shortcut.
ZIP codes by time zone at a glance
The examples in this guide come from ToolTrio’s bundled ZIP dataset for orientation. They are not an official USPS directory or a claim of complete 2026 ZIP coverage.
| Time zone | Generic | Standard / daylight | UTC offset | Coverage note |
|---|---|---|---|---|
| Eastern Time | ET | EST / EDT | UTC−5 / UTC−4 | Eastern U.S. and portions of split states |
| Central Time | CT | CST / CDT | UTC−6 / UTC−5 | Central U.S. and portions of split states |
| Mountain Time | MT | MST / MDT | UTC−7 / UTC−6 | Mountain region and portions of several states |
| Pacific Time | PT | PST / PDT | UTC−8 / UTC−7 | West Coast and portions of Idaho, Nevada and Oregon |
Eastern Time ZIP Codes
Eastern Time is commonly written ET, with EST during standard time and EDT during daylight time. The zone covers much of the East Coast and reaches into several states that are split between Eastern and another time zone.
Explore the dedicated guide: Eastern Time ZIP Codes
Central Time ZIP Codes
Central Time is CT, with CST and CDT as the standard and daylight designations. It covers a large part of the central United States and includes many states that also have ZIP records in neighboring zones.
Explore the dedicated guide: Central Time ZIP Codes
Mountain Time ZIP Codes
Mountain Time is MT, with MST and MDT commonly used for standard and daylight time. It covers Colorado, Montana, New Mexico, Utah, Wyoming and portions of several other states. Most of Arizona uses Mountain Standard Time year-round, which is one reason a ZIP-level lookup is preferable to a simple “state → time zone” rule.
Explore the dedicated guide: Mountain Time ZIP Codes
Pacific Time ZIP Codes
Pacific Time is PT, with PST and PDT as the standard and daylight designations. It covers California, Washington, Oregon, Nevada and part of Idaho in the current ToolTrio ZIP dataset.
Explore the dedicated guide: Pacific Time ZIP Codes
Why ZIP codes are better than state names for exact time-zone lookup
A state can cross a legal time-zone boundary. ZIP Codes, meanwhile, are postal delivery identifiers. They are different geographic systems. When an application needs to know the local time for a customer, employee, appointment, delivery or notification, resolving the actual ZIP to an IANA time zone is safer than storing only the state.
This is especially important around border regions and split states. A state-level rule may work for a broad visualization but fail for an individual customer record. The correct workflow is: input ZIP → resolve time zone → convert timestamp → display local time.
Standard time vs. daylight time
The names EST, CST, MST and PST refer to standard time. EDT, CDT, MDT and PDT refer to daylight time. The generic labels ET, CT, MT and PT are useful when the page or application does not need to state which seasonal abbreviation is active.
NIST lists the standard and daylight UTC offsets, while DOT oversees the legal time-zone framework. Do not hard-code a single offset into an application when the location observes daylight saving time. Use a time-zone-aware library and an IANA identifier.
How to find a ZIP code's time zone
- Open ZIP Code Time Zone Lookup.
- Enter the five-digit ZIP code.
- Read the returned time-zone identifier and display label.
- Use ZIP Code Time Zone Map when geographic context helps.
- Use Same Time Zone ZIPs if your goal is to find other ZIPs in the same zone.
For a postal address task, use USPS Address Format separately. Time-zone classification and postal-address formatting are related to a ZIP but are not the same operation.
ZIP Code Time Zone reference table
| Zone | Generic label | Seasonal abbreviations | UTC offset | Representative coverage |
|---|---|---|---|---|
| Eastern | ET | EST / EDT | UTC−5 / UTC−4 | New York, Pennsylvania, Ohio, Florida and more |
| Central | CT | CST / CDT | UTC−6 / UTC−5 | Texas, Illinois, Minnesota, Alabama and more |
| Mountain | MT | MST / MDT | UTC−7 / UTC−6 | Colorado, Utah, New Mexico, Montana and more |
| Pacific | PT | PST / PDT | UTC−8 / UTC−7 | California, Washington, Oregon, Nevada and part of Idaho |
Important edge cases
Arizona
Most of Arizona does not observe daylight saving time, so it remains on Mountain Standard Time while most other Mountain-zone locations move between standard and daylight time. The Navajo Nation follows daylight saving time. This makes Arizona a poor candidate for a blanket “Mountain Time always means MDT in summer” assumption.
Split states
Florida, Indiana, Kentucky, Michigan, Nebraska, North Dakota, South Dakota, Tennessee, Texas and other states have areas associated with different time zones. The exact list depends on the geographic or postal dataset being used.
ZIP Code vs. ZCTA
A USPS ZIP Code is not the same thing as a Census ZCTA. ZCTAs are statistical representations designed for Census analysis. If a page combines population, demographics and postal data, keep those concepts separate.
Postal data changes
A static article should not pretend to be a permanent official ZIP directory. ZIP records, city names, delivery areas and supporting datasets can change. ToolTrio therefore treats the article as a reference and the lookup tools as the operational path for an individual ZIP.
How the four zones differ for ZIP searches
The four-zone model is useful because it matches the way many people phrase local-time questions, but the boundaries are not simply four equal-width strips across the country. ZIP coverage reflects where postal delivery areas sit relative to those boundaries. A state can have a large majority of ZIPs in one zone and still have a smaller set in another. That is why a search result that gives only a state list can be incomplete.
For example, the ToolTrio dataset contains Central Time ZIP records in states that are also represented in Eastern or Mountain time. It also contains Mountain Time records in states such as Texas, Nebraska and South Dakota where only part of the state belongs to Mountain Time. Pacific Time similarly includes a portion of Idaho. These are exactly the cases where a ZIP-level result is more useful than a generic state label.
What the ZIP time-zone pages are designed to answer
The parent page answers the broad query: ZIP codes by time zone. The four child guides then answer the narrower searches: Eastern Time ZIP codes, Central Time ZIP codes, Mountain Time ZIP codes, and Pacific Time ZIP codes. Each child page adds a state-level table, representative ZIP examples, seasonal time rules, edge cases, and a direct link to the ZIP-level lookup.
This structure also keeps the site useful for people who arrive from different search intents. Someone researching a region can start with the parent. Someone searching “ZIP codes for Mountain Time” can land directly on the Mountain guide. Someone who already has a ZIP can skip the articles and use the lookup tool immediately.
ZIP-level data is more useful than a giant static list
A literal list of several thousand ZIP codes is difficult to search, difficult to maintain, and easy to make stale. A better reference combines a compact state table with an exact lookup tool. That is the approach used here. The tables show the shape of the data and representative records, while the live tools answer the specific ZIP question.
For developers, the same principle applies to an API or database. Store the ZIP as a string, keep leading zeroes, resolve it to an IANA identifier, and perform time conversion with a timezone-aware library. Do not infer UTC offsets by subtracting a fixed number from the clock. Daylight-saving rules make that approach unreliable.
Best way to use this guide
Use this parent page when your question is broad: ZIP codes by time zone, US ZIP codes by timezone, or Eastern vs. Central vs. Mountain vs. Pacific ZIP codes. Use the child pages when you need a deeper state-by-state reference. Use the live ZIP tools when you need an exact answer for one ZIP or a group of ZIPs.
Search questions this guide answers
This guide is useful for people searching ZIP codes by time zone, US ZIP codes by timezone, ZIP code time zone list, find ZIP codes by time zone, what ZIP codes are in Eastern Time, what ZIP codes are in Central Time, what ZIP codes are in Mountain Time, or what ZIP codes are in Pacific Time. These are natural variations of the same research task, so they are covered together rather than split into near-duplicate pages.
Frequently asked questions
What are the four main U.S. time zones?
For the contiguous United States, the four primary zones are Eastern, Central, Mountain and Pacific. The United States also has Alaska, Hawaii-Aleutian and other time zones in states and territories.
Can a ZIP code cross a time-zone boundary?
The safest answer is to resolve the ZIP record rather than assume that the state determines the zone. ZIP Codes are postal constructs and time zones are legal geographic boundaries, so the two systems should not be treated as identical.
What ZIP codes are in Mountain Time?
Mountain Time ZIP Codes occur across Colorado, Montana, New Mexico, Utah, Wyoming and portions of several other states. The dedicated Mountain guide explains the regional coverage, while the ZIP Code Time Zone Lookup is the better choice when you already have one ZIP to check.
What is the difference between MST and MDT?
MST is Mountain Standard Time and MDT is Mountain Daylight Time. The generic term Mountain Time can refer to either depending on the location's current DST status.
Should a website store EST, CST, MST or PST?
For software, storing an IANA time-zone identifier is usually more robust because it carries the location's time-zone rules. The abbreviation can be generated for display.
2026 data and accuracy note
Reviewed October 3, 2026. The time-zone rules in this guide are checked against the current IANA Time Zone Database release 2026e, released September 29, 2026, plus the U.S. Department of Transportation’s official time-zone framework and NIST’s U.S. time-zone offset table. The ZIP examples are read from ToolTrio’s local static ZIP dataset; this article does not call an API at page load. Because there is no single USPS table that publishes a ZIP-to-time-zone directory, ToolTrio does not label its local ZIP examples as an official USPS time-zone list.
Sources and methodology
- U.S. Department of Transportation: Uniform Time — official federal overview of time zones and DOT oversight.
- U.S. Department of Transportation / Data.gov: Time Zones dataset — geospatial time-zone boundaries.
- NIST: Local Time FAQs — standard/daylight abbreviations and UTC offsets.
- ToolTrio ZIP dataset: current records bundled with this project, grouped by IANA time-zone identifier for the tables and charts above.
Editorial methodology
This guide intentionally separates three layers: official time-zone rules, ZIP-level data, and derived summaries. DOT and NIST are used for the time-zone explanation. ToolTrio's ZIP dataset is used for the record counts and examples. A summary count is not presented as an official USPS statistic.