README for “Time Zones 2019-Present” dataset. U.S. Department of Transportation (DOT), Bureau of Transportation Statistics (BTS); U.S. Department of Transportation (USDOT), Bureau of Transportation Statistics (BTS) [distributor] 2025-06-09 ---------------------------------------------------------------- LINKS TO DATASET ---------------------------------------------------------------- A. Dataset archive link: https://doi.org/10.21949/1403512 B. NTAD catalog dataset link (Current Year): https://doi.org/10.21949/1522274 ---------------------------------------------------------------- SUMMARY OF DATASET ---------------------------------------------------------------- The Time Zones 2019-Present dataset is from the Bureau of Transportation Statistics (BTS), and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics’s (BTS's) National Transportation Atlas Database (NTAD). This layer is a digital representation of the geographic boundaries of the nine time zones that cover the United States and its territories (the Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii–Aleutian, Samoa, and Chamorro time zones). The U.S. Department of Transportation (DOT) oversees the Nation's time zones and the uniform observance of Daylight-Saving Time. The oversight of time zones was assigned to DOT due to the importance of time coordination for transportation related activities. The time zones were established by the Standard Time Act of 1918 and amended by the Uniform Time Act of 1966. Time zones in the U.S. are defined in the U.S. Code, Title 15, Chapter 6, Subchapter IX - Standard Time. The time zone boundaries are defined in the Code of Federal Regulations (CFR), Title 49, Subtitle A, Part 71 - Standard Time Zone Boundaries. Segments used to compile the geospatial layer were derived from the CFR’s time zone descriptions (https://www.ecfr.gov/current/title-49/subtitle-A/part-71). Descriptions consist of segments referencing administrative boundaries, infrastructure, natural features, and geodesic lines. These segments are contained in various data layers in the National Geospatial Data Asset (NGDA) portfolio, the federal government’s authoritative geospatial data repository. Referenced segments were extracted from their NGDA and then merged to form continuous boundaries. In instances where there were multiple scales for a given dataset, the largest scale or most detailed layer was used. The standard time of the Atlantic zone is the Coordinated Universal Time (UTC) minus 4 hours; Eastern zone is UTC minus 5 hours; Central zone is UTC minus 6 hours; Mountain zone is UTC minus 7 hours; Pacific zone is UTC minus 8 hours; Alaska zone is UTC minus 9 hours; Hawaii–Aleutian zone is UTC minus 10 hours; Samoa zone is UTC minus 11 hours; and Chamorro zone is UTC plus 10 hours. For more information, please visit: https://doi.org/10.21949/1519143. ---------------------------------------------------------------- TABLE OF CONTENTS ---------------------------------------------------------------- A. General Information B. Sharing/Access & Policies Information C. Data and Related File Overview D. Methodological Information E. Data-Specific Information for: Time Zones 2019-Present [datasets] F. Update Log ---------------------------------------------------------------- A. GENERAL INFORMATION ---------------------------------------------------------------- 0. Title of Dataset: Time Zones 2019-Present [dataset] 1. Description of Dataset: The Time Zones 2019-Present dataset is from the Bureau of Transportation Statistics (BTS), and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics’ (BTS's) National Transportation Atlas Database (NTAD). This layer is a digital representation of the geographic boundaries of the nine time zones that cover the United States and its territories (the Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii–Aleutian, Samoa, and Chamorro time zones). The U.S. Department of Transportation (DOT) oversees the Nation's time zones and the uniform observance of Daylight-Saving Time. The oversight of time zones was assigned to DOT due to the importance of time coordination for transportation related activities. The time zones were established by the Standard Time Act of 1918 and amended by the Uniform Time Act of 1966. Time zones in the U.S. are defined in the U.S. Code, Title 15, Chapter 6, Subchapter IX - Standard Time. The time zone boundaries are defined in the Code of Federal Regulations (CFR), Title 49, Subtitle A, Part 71 - Standard Time Zone Boundaries. Segments used to compile the geospatial layer were derived from the CFR’s time zone descriptions (https://www.ecfr.gov/current/title-49/subtitle-A/part-71). Descriptions consist of segments referencing administrative boundaries, infrastructure, natural features, and geodesic lines. These segments are contained in various data layers in the National Geospatial Data Asset (NGDA) portfolio, the federal government’s authoritative geospatial data repository. Referenced segments were extracted from their NGDA and then merged to form continuous boundaries. In instances where there were multiple scales for a given dataset, the largest scale or most detailed layer was used. The standard time of the Atlantic zone is the Coordinated Universal Time (UTC) minus 4 hours; Eastern zone is UTC minus 5 hours; Central zone is UTC minus 6 hours; Mountain zone is UTC minus 7 hours; Pacific zone is UTC minus 8 hours; Alaska zone is UTC minus 9 hours; Hawaii–Aleutian zone is UTC minus 10 hours; Samoa zone is UTC minus 11 hours; and Chamorro zone is UTC plus 10 hours. For more information, please visit: https://doi.org/10.21949/1519143. 2. Dataset archive link: https://doi.org/10.21949/1403512 3. Authorship Information: Principal Data Creator or Data Manager Contact Information Institution: U.S. Department of Transportation (DOT), Bureau of Transportation Statistics (BTS) Address: 1200 New Jersey Ave SE, Washington D.C. 20590 Contact: bts@dot.gov Data Distributor Contact Information Name: National Transportation Atlas Database (NTAD) Institution: U.S. Department of Transportation (USDOT), Bureau of Transportation Statistics (BTS), Office of Spatial Analysis and Visualization (OSAV) Address: 1200 New Jersey Ave. SE, Washington D.C. 20590 Email: ntad@dot.gov 4. Date of data collection and update interval: This dataset is updated as needed. This dataset is updated as needed. Dataset Manager is contacted to verify changes to data resulting in NTAD update. The metadata is updated in the same manner. For the most recent data, please visit the NTAD catalog at https://doi.org/10.21949/1522274 5. Geographic location of data collection: United States of America 6. Information about funding sources that supported the collection of the data: Bureau of Transportation Statistics (BTS), U.S. Department of Transportation (DOT) ---------------------------------------------------------------- B. SHARING/ACCESS & POLICIES INFORMATION ---------------------------------------------------------------- 0. Recommended citation for the data: U.S. Department of Transportation (DOT), Bureau of Transportation Statistics (BTS), U.S. Department of Transportation, Bureau of Transportation Statistics (BTS) [distributor]. Time Zones 2019-Present [datasets]. 1. Licenses/restrictions placed on the data: These data are in the Public Domain. 2. Was data derived from another source?: Yes. The Office of General Council (OGC)'s time zone boundary document was counsulted during the creation of this dataset. 3. This document was created to meet the requirements enumerated in the U.S. Department of Transportation's 'Plan to Increase Public Access to the Results of Federally-Funded Scientific Research' Version 1.1 << https://doi.org/10.21949/1520559 >> and guidelines suggested by the DOT Public Access website << https://doi.org/10.21949/1503647 >>, in effect and current as of December 03, 2020. ---------------------------------------------------------------- C. DATA & RELATED FILE OVERVIEW ---------------------------------------------------------------- 1. File List for the Time Zones 2019-Present dataset A. Filename: bts_NTAD_Time_Zones_DMP_20250609.pdf Short description: A PDF file containing the Data Management Plan that was created for current and future management of the data and associated files. B. Filename: bts_NTAD_Time_Zones_README_20250609.txt Short description: The README.txt file that includes human-readable information about the data, variable definitions, contact information, and other contextual information. The file you are reading now. C. File List for the Time_Zones_NTAD2019_Present.zip collection. Ca. File List for NTADXXXX_GDB_Final_Time_Zones_XXXX_XX_XX.zip collection Ca 1. Filename: NTADXXXX_GDB_Final_Time_Zones_XXXX_XX_XX.gdb.zip (Folder) Short description: Compressed file folders containing the geospatial data for Time Zones 2019-Present dataset. File folders are classified by NTAD publication year and data vintage year or date respectively. Geodatabase (GDB) folders contain all the necessary components to view and otherwise interact with their data. Ca 2. Filename: Time_Zones.xml Short description: Extensible Markup Language (XML) files containing key metadata and documentation information such as methodology, procedures, etc. Ca 3. Filename: T_Zone.xlsx Short description: Excel spreadsheet containing the dataset's data dictionary including attribute field names and definitions for fields and applicable values. ---------------------------------------------------------------- D. METHODOLOGICAL INFORMATION ---------------------------------------------------------------- 1. Description of methods used for collection/generation of data: The Time Zones dataset was created by consulting the Office of General Council (OGC)'s time zone boundary document. Made a list of geographic from the document that were then verified from authoritative sources i.e. Census, BLS, USACE, etc. All components were added in ArcGIS along with manually generated lines of longitude. Features were traced to create boundary line, then transforms into polygons. Discrepancies that were found were communicated back to OGC for potential future rule changes to the Code of Federal Regulations Standard Time Zone Boundaries. OSAV reviews then GIS experts peer review the data specific to their extertise. BTS conducts a final peer review and the data is published. 2. Instrument- or software-specific information needed to interpret the data: The shapefile data can be opened with Esri ArcGIS and any GIS software package. File geodatabase data can only be opened with Esri ArcGIS. The documentation files can be opened with any basic text editor. ---------------------------------------------------------------- E. DATA-SPECIFIC INFORMATION ---------------------------------------------------------------- 1. Time Zones data table Due to the size of the data, it is not described in detail here. Review the data dictionary present in the data folders for information on the data table. A. Number of variables (columns): The data dictionary found in T_Zone.xlsx provides definitions for the variables B. Data Dictionary/Variable List: Because of the large number of variables, please refer to the Data Dictionary found within the file T_Zone.xlsx for names, definitions, and formats of variables. C. Missing data codes: None ---------------------------------------------------------------- F. UPDATE LOG ---------------------------------------------------------------- This bts_Time_Zones_20250609_README.txt file was originally created on 2025-05-28 by Dominic Menegus, Geographer, dominic.menegus@dot.gov [Note changes or update to the readme.txt file, e.g.:] 2025-06-09: Original file created 2025-12-30: DOI added