The 516 Area Code: 7 Crucial Facts About Long Island's Original Number And The New 363 Overlay

The 516 area code is one of New York State's most historic and recognizable telephone codes, intrinsically linked to the affluent and vibrant region of Nassau County on Long Island. As of the current date, December 17, 2025, the 516 area code is still the primary identifier for this region, but it now operates in an overlay complex with a brand-new code, requiring all residents and businesses to be aware of significant dialing changes that have been fully implemented. This comprehensive guide will break down the essential facts about the 516 area code, its geographic coverage, its rich history, and the critical details of the 363 overlay that has permanently changed how you make calls in this part of New York. The introduction of an overlay complex is a clear sign of population and telecommunication growth, signaling that the original supply of 516 numbers has been exhausted. Understanding the transition to the new 363 area code is vital for anyone living in, moving to, or doing business with Nassau County, ensuring you avoid dropped calls and stay connected with communities like Hempstead, Levittown, and Freeport.

1. The 516 Area Code Covers Nassau County, Long Island, New York

The 516 area code’s geographic footprint is precisely defined: it covers the entirety of Nassau County, a major suburban region immediately east of New York City (Queens County). This area is the westernmost part of Long Island, known for its high quality of life, proximity to Manhattan, and distinct suburban character. Key cities and towns within the 516 Numbering Plan Area (NPA) include:

• Hempstead
• Levittown
• Freeport
• Hicksville
• Garden City
• Valley Stream
• Long Beach
• Glen Cove

While the 516 area code is primarily associated with Nassau County, it historically covered the entirety of Long Island before a split in 1999.

2. It Operates in the Eastern Time Zone (ET)

The 516 area code is situated within the Eastern Time Zone (ET). This means that during the year, it observes Eastern Standard Time (EST) and Eastern Daylight Time (EDT) when daylight saving is in effect. If you are calling the 516 area code from outside the Eastern Time Zone, you will need to adjust for the time difference, which is typically three hours ahead of Pacific Time (PT).

3. The 516 Code Was Split to Create the 631 Area Code

The history of the 516 area code is a classic example of number exhaustion due to rapid population growth. It was initially created in 1951, splitting off from the 914 area code, and covered all of Long Island, encompassing both Nassau and Suffolk Counties. However, by the late 1990s, the demand for telephone numbers in the rapidly developing region necessitated a split. In 1999, the 516 area code was split, and the eastern portion, Suffolk County, was assigned the new 631 area code. This split left the 516 area code to exclusively cover the region of Nassau County, which remains its coverage today.

4. Mandatory 10-Digit Dialing is Now Required

A major and permanent change for all residents and businesses in the 516 area code is the requirement for 10-digit dialing for all local calls. This change was mandated by the New York Public Service Commission (PSC) as a necessary step before the introduction of the new overlay code. The mandatory 10-digit dialing began on October 24, 2021. This means that even if you are calling a number within the same 516 area code, you must dial the full 10-digit number (516 + seven-digit number). Failure to dial all 10 digits will result in a dropped call or an error message.

5. The New Overlay Area Code is 363

The most recent and critical update for the 516 area code is the introduction of an all-services overlay area code: 363. This overlay was approved to ensure a continuing supply of new telephone numbers once the 516 number pool was exhausted. The 363 area code was officially introduced on January 20, 2023, and serves the exact same geographic region as the 516 area code—Nassau County. An "overlay" means that two or more area codes serve the same geographic area. New customers requesting a phone line in Nassau County may now be assigned a number with the 363 area code. Existing 516 numbers were not changed, but the new 363 numbers now coexist within the same region.

6. Key Entities and Communities in the 516/363 Region

The 516 area code is synonymous with the diverse and historically significant region of Nassau County. Topical authority for this region includes a variety of communities and institutions:

• The Town of Hempstead: The largest township in Nassau County by population, encompassing major communities like Levittown and Freeport.
• Hicksville: A major commercial hub and transportation center on Long Island.
• Garden City: Known for its planned layout, beautiful architecture, and as the location of Adelphi University.
• Long Beach: A popular city located on a barrier island, famous for its boardwalk and beaches.
• Nassau Community College: One of the largest single-campus community colleges in the state of New York.

These entities highlight the blend of suburban living, educational centers, and coastal recreation that defines the 516 area.

7. What the 363 Overlay Means for Businesses

For businesses operating within Nassau County, the 363 overlay has several practical implications: * Updated Marketing: Business owners must ensure all advertising, stationery, websites, and signage include the full 10-digit number for both 516 and 363 numbers. * Reprogramming Equipment: Any equipment that auto-dials or stores numbers, such as alarm systems, PBX systems, speed dialers, and fax machines, must be checked and reprogrammed to dial 10 digits for all local calls. * New Number Assignment: Businesses requesting new lines or additional numbers should expect to receive a 363 area code, not a 516. The transition to an overlay system is a permanent change that affects the telecommunications infrastructure of the entire Nassau County region. By embracing the 10-digit dialing requirement and recognizing the new 363 code, residents and businesses can ensure seamless communication for years to come.