Time Zones

The Time Zones dataset was compiled on October 04, 2019 and was updated January 05, 2023 from the Bureau of Transportation Statistics (BTS) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) 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. A data dictionary, or other source of attribute information, is accessible at https://doi.org/10.21949/1529083本时区数据集编制于2019年10月4日，于2023年1月5日基于美国运输统计局（Bureau of Transportation Statistics, BTS）数据源更新，隶属于美国交通部（U.S. Department of Transportation, USDOT）/美国运输统计局（BTS）国家交通地图集数据库（National Transportation Atlas Database, NTAD）。该数据集图层为覆盖美国及其属地的9个时区的地理边界数字化表达，涵盖大西洋时区、东部时区、中部时区、山地时区、太平洋时区、阿拉斯加时区、夏威夷-阿留申时区、萨摩亚时区以及查莫罗时区。美国交通部（DOT）负责监管美国全国时区及夏令时的统一执行。鉴于时间协调对交通运输相关活动的重要性，时区监管职责被划归至美国交通部。美国时区由1918年《标准时间法案》确立，并经1966年《统一时间法案》修订。美国时区的相关规定见于《美国法典》第15编第6章第IX分章——标准时间。时区边界的规定则见于《联邦法规汇编》（Code of Federal Regulations, CFR）第49编A分册第71部分——标准时区边界。用于构建该地理空间图层的边界段均源自《联邦法规汇编》中关于时区的描述（https://www.ecfr.gov/current/title-49/subtitle-A/part-71）。此类描述包含行政边界、基础设施、自然地貌及测地线相关的边界段，且均收录于美国联邦政府权威地理空间数据仓库——国家地理空间数据资产（National Geospatial Data Asset, NGDA）合集的各类数据图层中。研究人员从NGDA相关图层中提取所需边界段，再将其拼接为连续的时区边界。若同一数据集存在多种比例尺版本，则选用比例尺最大、细节最丰富的图层。各时区标准时间如下：大西洋时区为协调世界时（Coordinated Universal Time, UTC）减4小时；东部时区为UTC减5小时；中部时区为UTC减6小时；山地时区为UTC减7小时；太平洋时区为UTC减8小时；阿拉斯加时区为UTC减9小时；夏威夷-阿留申时区为UTC减10小时；萨摩亚时区为UTC减11小时；查莫罗时区为UTC加10小时。如需获取更多信息，请访问：https://doi.org/10.21949/1519143。数据字典或其他属性信息可通过以下链接获取：https://doi.org/10.21949/1529083。