Area Code Time Zones: Which Zone Is Your Area Code In, and Which 22 Split Between Two?

How many US area codes are in each time zone

The North American Numbering Plan Administrator (NANPA) publishes the authoritative list of area codes in its NPA reports and as a CSV file with a time zone field for each code. We read the file dated October 24, 2026. It has 378 geographic area codes in service in the United States, counting the 50 states, DC and five territories (Puerto Rico, the Virgin Islands, Guam, the Northern Mariana Islands and American Samoa). The zone breakdown is below.

That is 356 codes in one zone and 22 in two. The 18 Mountain codes are 303, 307, 385, 406, 435, 480, 505, 520, 575, 602, 623, 719, 720, 748, 801, 928, 970 and 983. Each has its own page on this site with the cities it covers and the current local time, starting from the area code directory. For Eastern, Central and Pacific codes that are not on a split list, the code alone is enough to know the zone.

The 22 area codes that straddle two time zones

NANPA's file gives each code one zone field, so a code that covers ground on both sides of a time zone line carries two letters. The file does not say which towns or exchanges are on which side. For those, check the town and not the code.

Our pages for the split codes say so: area code 850 spans Eastern and Central time, and so do 270 and 423. The Mountain and Pacific split is 208 and 541. 605 and 915 split Central and Mountain.

Where the zone lines actually run

The lines are legal, not informal. The Department of Transportation sets them in 49 CFR Part 71, which describes each boundary by rivers, county lines and township lines, and which puts any municipality sitting on a boundary line in the zone on the eastern or southern side: Central on the Eastern–Central line (§ 71.5(h)), Mountain on the Central–Mountain line (§ 71.7(g), with Murdo, South Dakota, as the exception that is Central) and Mountain on the Mountain–Pacific line (§ 71.9(d)). A few examples from the rule text show why a split code needs a town, not just a code:

• Florida (§ 71.5(f)): the Eastern–Central line follows the Apalachicola River and then the west line of Gulf County to the Gulf of Mexico. The Panhandle west of that line is on Central time, which is where 850 and its overlay 448 get their second zone.
• Michigan, Indiana, Kentucky and Tennessee (§ 71.5(a)–(d)): the line follows county lines, including Gogebic, Iron, Dickinson and Menominee in Michigan's Upper Peninsula; LaPorte, Starke, Jasper, Newton, Gibson, Warrick, Spencer and Perry in Indiana; Meade, Hardin, Larue, Taylor, Casey, Pulaski and Wayne in Kentucky; and Scott, Morgan, Roane, Rhea and Hamilton in Tennessee. One code can sit on both sides of it.
• The Dakotas and Kansas (§ 71.7): the Central–Mountain line follows the Missouri River for much of its length through the Dakotas. In Kansas it runs around Sherman, Wallace, Greeley and Hamilton counties, which are the Mountain-time part of the state.
• Texas (§ 71.7(e)): the line follows the Texas–New Mexico border to the east line of Hudspeth County, so El Paso and Hudspeth counties are Texas's Mountain-time counties.
• Idaho, Oregon and Nevada (§ 71.9): the Mountain–Pacific line follows the Salmon River in Idaho and then Oregon's Malheur County lines, and it carves out the city of West Wendover, Nevada, as Mountain time inside an otherwise Pacific state.

Because NANPA records only the code, a split code can include a second zone that holds few of its numbers. The safe reading is that the code does not decide the zone, and the town does.

Arizona, Hawaii and the territories: zones that do not change clocks

A zone name is not enough, because some places keep one clock all year. Under the Uniform Time Act, states may exempt themselves from daylight saving time, and the U.S. Department of Transportation says it is not observed in Hawaii, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, the Virgin Islands and most of Arizona (DOT). NIST adds that the Navajo Nation inside Arizona does observe it (NIST).

In practice, Arizona's codes (480, 520, 602, 623 and 928) are on Mountain standard time all year. That matches Mountain time in winter and Pacific time in summer. Puerto Rico and the Virgin Islands are on Atlantic standard time, UTC-4 all year, which equals Eastern daylight time in summer and is an hour ahead of Eastern in winter. Hawaii, at UTC-10, is five hours behind Eastern in winter and six in summer. In 2026 daylight time ends at 2 a.m. on Sunday, November 1 (49 CFR 71.2), so Eastern-to-Arizona gaps change that weekend.

A worked example: 10 a.m. in New York

NANPA lists 212 as Eastern, 312 as Central, 303 as Mountain, 213 as Pacific, 907 as Alaska and 808 as Hawaii. While daylight time is in effect, as it is today, 10 a.m. in 212 is 9 a.m. in 312, 8 a.m. in 303, 7 a.m. in 213, 6 a.m. in 907 and 4 a.m. in 808. Arizona's 602 is also on 7 a.m. because it is on Mountain standard time. After the clocks go back on November 1, the first five hold their one-hour steps, but 808 is at 5 a.m. and 602 is at 8 a.m., an hour ahead of the Pacific code. The same arithmetic is what the calling-hours rules use, and our calling-hours guide turns it into a table.

Why an area code is still not a location

A code tells you where the number was first assigned. It does not tell you where the person is now. The CFPB's debt-collection rule says plainly that mobile numbers “are not associated with a place,” and its own examples assume a consumer can have a mobile number with an Eastern area code and a home in the Pacific zone (Regulation F, 12 CFR 1006.6). The FCC's porting guide says you can keep your number when you change providers and stay in the same geographic area, and that you may not be able to if you move to a new one.

Callers can also fake the code. The FCC describes “neighbor spoofing,” which shows a number similar to your own so you are more likely to answer (FCC). A call that appears to come from your own area code tells you what the caller wanted you to see. Our guide to neighbor spoofing covers it, and the area codes to avoid article looks at what the complaint data says about area codes.

Using the zone for calling hours

Telemarketing and debt-collection rules count 8 a.m. to 9 p.m. by the clock where the person called is. If all you have is an area code, use the code's zone as a starting point and, for a split code or a mobile number, stay inside the window that is lawful in every possible zone. The calling-hours guide has the rule text, a conversion table and six state laws with different hours.

To check a zone quickly: find the code in the area code directory, read the “Local time” line on its page, and for a split code look at the cities listed to see which side your town is on. Or start from the state: the Arizona, Hawaii and Kentucky pages link the codes that serve them.

Sources

1. NANPA — NPA reports
2. NANPA — NPA database CSV (file dated October 24, 2026)
3. U.S. Department of Transportation — Daylight Saving Time
4. NIST — Local time FAQs
5. 49 CFR Part 71 — standard time zone boundaries (eCFR)
6. CFPB — 12 CFR 1006.6, Regulation F, and official interpretation
7. FCC — Porting: keeping your phone number when you change providers
8. FCC — Caller ID spoofing

Related

• What time can telemarketers call?
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• Neighbor spoofing
• All US area codes

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