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Time Zones of the United States

Metadata also available as - [Outline] - [Parseable text] - [XML] - [DIF]

Frequently-anticipated questions:


What does this data set describe?

Title: Time Zones of the United States
Abstract:
This map layer portrays the time zones of the United States, Puerto Rico, and the U.S. Virgin Islands. Also included are the Greenwich Mean Time offset, and areas in the U.S. where daylight saving time is observed. This is a revised version of the June 2005 map layer.
  1. How should this data set be cited?

    National Atlas of the United States, 200906, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: 170
    East_Bounding_Coordinate: -64
    North_Bounding_Coordinate: 72
    South_Bounding_Coordinate: 17

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1972
    Ending_Date: 2009
    Currentness_Reference: Ground condition

  5. What is the general form of this data set?

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • GT-polygon composed of chains (2835)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000278. Longitudes are given to the nearest 0.000278. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?

    Time zones (described by timeznp020.dbf)
    Geographic regions within which the same standard time is used. (Source: National Atlas of the United States)

    Shape
    The representation of the entity in the data. (Source: National Atlas of the United States)

    ValueDefinition
    Polygon2-dimensional element.

    Area
    The size of the shape in coverage units. In the distributed file, coverage units represent square decimal degrees. (Source: National Atlas of the United States)

    Range of values
    Minimum:0.000
    Maximum:306.573

    Perimeter
    The perimeter of shape in coverage units. In the distributed file, coverage units represent decimal degrees. (Source: National Atlas of the United States)

    Range of values
    Minimum:0.010
    Maximum:374.768

    Timeznp020
    Internal feature number. (Source: National Atlas of the United States)

    Range of values
    Minimum:2
    Maximum:2835

    Timezone
    The name of the time zone. (Source: National Atlas of the United States)

    ValueDefinition
    AlaskaThe time zone that includes most of Alaska, as defined in the Code of Federal Regulations, Title 49--Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    AtlanticThe time zone that includes Puerto Rico and the U.S. Virgin Islands, as defined in the Code of Federal Regulations, Title 49-- Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    CentralThe time zone that is east of the Mountain time zone and west of the Eastern time zone, as defined in the Code of Federal Regulations, Title 49--Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    EasternThe time zone for the eastern continental United States, between the Atlantic and Central time zones, as defined in the Code of Federal Regulations, Title 49--Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    Hawaii-AleutianThe time zone that includes most of the Aleutian Islands and Hawaii, as defined in the Code of Federal Regulations, Title 49- Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    MountainThe time zone that is east of the Pacific time zone and west of the Central time zone, as defined in the Code of Federal Regulations, Title 49--Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.
    PacificThe time zone for the western continental United States, west of the Mountain time zone, as defined in the Code of Federal Regulations, Title 49--Transportation, Subtitle A--Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries.

    Gmt_offset
    The number of hours the time is offset from Greenwich Mean Time. (Source: National Atlas of the United States)

    Range of values
    Minimum:-10
    Maximum:-4

    Gmt_dst_of
    The number of hours the time is offset from Greenwich Mean Time when daylight saving time is in effect. (Source: National Atlas of the United States)

    ValueDefinition
    noDaylight saving time is not observed.

    Range of values
    Minimum:-9
    Maximum:-3

    Symbol
    A code used to determine polygon symbolization for map display. (Source: National Atlas of the United States)

    ValueDefinition
    ALAlaska time zone.
    ATAtlantic time zone.
    CECentral time zone.
    EAEastern time zone.
    EAnoEastern time zone; daylight saving time not observed.
    HAHawaii-Aleutian time zone.
    HAnoHawaii-Aleutian time zone; daylight saving time not observed.
    MOMountain time zone.
    MOnoMountain time zone; daylight saving time not observed.
    PAPacific time zone.


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

    • National Atlas of the United States

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Jay Donnelly
    National Atlas of the United States
    12201 Sunrise Valley Drive
    Reston, VA 20192

    703-648-5395 (voice)
    atlasmail@usgs.gov


Why was the data set created?

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Atlas of the United States or the U.S. Geological Survey in the use of these data.


How was the data set created?

  1. From what previous works were the data drawn?

    CFR-TZ (source 1 of 22)
    National Archives and Records, 1997, Code of Federal Regulations, Title 49--Transportation, Subtitle A-- Office of the Secretary of Transportation, Part 71--Standard Time Zone Boundaries: National Archives and Records Administration, Washington, DC.

    Online Links:

    Type_of_Source_Media: Online
    Source_Contribution: Spatial and attribute information

    NWS-CNTY (source 2 of 22)
    Service, National Weather , 1999, Counties of the U.S.: National Weather Service, Silver Spring, MD.

    Online Links:

    Type_of_Source_Media: Online
    Source_Contribution: Spatial and attribute information

    ATLAS-CNTY (source 3 of 22)
    National Atlas of the United States, 1998, County Boundaries of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-HY (source 4 of 22)
    National Atlas of the United States, 1998, Hydrography Features of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-PL (source 5 of 22)
    National Atlas of the United States, 199907, Public Land Survey System of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Internal file
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-RR (source 6 of 22)
    National Atlas of the United States, 1998, Railroads of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    GooseCreek-100K (source 7 of 22)
    U.S. Geological Survey, 1985, Goose Creek, NE: U.S. Geological Survey, Reston, VA.

    Type_of_Source_Media: Paper
    Source_Scale_Denominator: 100000
    Source_Contribution: Spatial information

    Valentine-100K (source 8 of 22)
    U.S. Geological Survey, 1985, Valentine, SD-NE: U.S. Geological Survey, Reston, VA.

    Type_of_Source_Media: Paper
    Source_Scale_Denominator: 100000
    Source_Contribution: Spatial information

    ATLAS-TZ (source 9 of 22)
    National Atlas of the United States, 200001, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

    TZ-SPLIT (source 10 of 22)
    Service, National Weather , 1998, CONUS Time Zones - Splits: National Weather Service, Silver Spring, MD.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    C_05FE02 (source 11 of 22)
    Service, National Weather , 2002, CONUS and Non CONUS Counties: National Weather Service, Silver Spring, MD.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-TZ02 (source 12 of 22)
    National Atlas of the United States, 200205, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

    ATLAS-CNTY01 (source 13 of 22)
    National Atlas of the United States, 200208, County Boundaries of the United States, 2001: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-TZ03 (source 14 of 22)
    National Atlas of the United States, 200311, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

    ATLAS-ROAD (source 15 of 22)
    National Atlas of the United States, 199911, Major Roads of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-TZ0401 (source 16 of 22)
    National Atlas of the United States, 200401, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

    NIST-TF (source 17 of 22)
    National Institute of Standards and Technology, Unknown, Time and Frequency from A to Z: National Institute of Standards Technology, Boulder, CO.

    Online Links:

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Attibute information

    ATLAS-FEDLAND (source 18 of 22)
    National Atlas of the United States, 200310, Federal Lands and Indian Reservations of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-TZ0409 (source 19 of 22)
    National Atlas of the United States, 200409, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

    ATLAS-STATES (source 20 of 22)
    National Atlas of the United States, 200506, State Boundaries of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-CNTY02 (source 21 of 22)
    National Atlas of the United States, 200506, County Boundaries of the United States, 2001: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial information

    ATLAS-TZ0506 (source 22 of 22)
    National Atlas of the United States, 200506, Time Zones of the United States: National Atlas of the United States, Reston, VA.

    Type_of_Source_Media: Online
    Source_Scale_Denominator: 2000000
    Source_Contribution: Spatial and attribute information

  2. How were the data generated, processed, and modified?

    Date: 10-Jan-2000 (process 1 of 7)
    Following the written descriptions in CFR-TZ, features coincident with time zone lines were extracted from the National Atlas map layers (ATLAS-CNTY, ATLAS-HY, ATLAS-PL, ATLAS-RR). The features were merged into a separate Arc/INFO coverage. Where there were no coincident features, 1:100,000-scale topographic maps (GooseCreek-100K and Valentine-100K) and county data sets (NWS-CNTY) were used as references to digitize the time zone boundaries. The NWS-CNTY data set was also used as a reference to define time zones where counties were divided by standard time zone boundaries.

    Data sources used in this process:

    • CFR-TZ
    • NWS-CNTY
    • ATLAS-CNTY
    • ATLAS-HY
    • ATLAS-PL
    • ATLAS-RR
    • GooseCreek-100K
    • Valentine-100K

    Data sources produced in this process:

    • ATLAS-TZ

    Date: 2002 (process 2 of 7)
    Several corrections were made using data obtained from the National Weather Service website. Counties that are split between two time zones were edited using TZ-SPLIT. Other corrections were made using C_05FE02. These corrections are:
    1) addition of a small portion of northwestern Cuberson County, TX to
       the Mountain time zone.
    2) adjustment of  a small portion of the Mountain/Central time zone
       boundary along the 138N and 139N Township line to the Missouri River
       just south of Mandan, Morton County, North Dakota.
    3) addition of Wayne County, KY, Morgan County, TN, Harrison County,
       IN, Floyd County, IN, and Clark County, IN to the Eastern time zone.
    
    In addition, some boundary adjustments were made using National Atlas counties, ATLAS-CNTY, to ensure alignment with county boundaries.

    Data sources used in this process:

    • ATLAS-TZ
    • TZ-SPLIT
    • C_05FE02
    • ATLAS-CNTY

    Data sources produced in this process:

    • ATLAS-TZ02

    Date: Nov-2003 (process 3 of 7)
    The time zone boundary between the Central time zone and the Mountain time zone was adjusted to place Jones County, Mellette County, and Todd County, SD in the Central time zone. County boundaries were extracted from ATLAS-CNTY01 and used to provide the new time zone boundary.

    Data sources used in this process:

    • ATLAS-TZ02
    • ATLAS-CNTY01

    Data sources produced in this process:

    • ATLAS-TZ03

    Date: Jan-2004 (process 4 of 7)
    The time zone boundary between the Central time zone and the Mountain time zone was adjusted to place all of Morton County, ND and part of Sioux County, ND east of highway 31 in the Central time zone. County boundaries from ATLAS-CNTY01 and a portion of highway 31 from ATLAS-ROAD were extracted and used to provide the new time zone boundary.

    Data sources used in this process:

    • ATLAS-TZ03
    • ATLAS-CNTY01
    • ATLAS-ROAD

    Data sources produced in this process:

    • ATLAS-TZ0401

    Date: Sep-2004 (process 5 of 7)
    Relying on the information from NIST-TF, the Navajo Indian Reservation within the State of Arizona was brought into ATLAS-TZ0401 from ATLAS- FEDLAND and coded as observing Daylight Saving Time. The Hopi Indian Reservation remains as not observing Daylight Saving Time.

    Data sources used in this process:

    • NIST-TF
    • ATLAS-FEDLAND
    • ATLAS-TZ0401

    Data sources produced in this process:

    • ATLAS-TZ0409

    Date: Jun-2005 (process 6 of 7)
    To bring the shorelines into better alignment with the rest of the Atlas data and to add 3 missing islands in Puerto Rico, the shorelines in ATLAS-TZ0409 were replaced with shorelines from ATLAS-STATES.

    Data sources used in this process:

    • ATLAS-STATES
    • ATLAS-TZ0409

    Date: Jun-2009 (process 7 of 7)
    Following the written descriptions in CFR-TZ, the time zone boundary between the Central time zone and the Eastern time zone was adjusted to place all of Knox County, Daviess County, Martin County, Pike County, Dubois County, and Pulaski County, IN in the Eastern time zone. The time zone boundary between the Hawaii-Aleutian time zone and the Alaska time zone was adjusted to place the part of the Aleutian Islands that is west of 169degrees 30 minutes west longitude in the Hawaii-Aleutian time zone, and the Pribilof Islands in the Alaska time zone. County boundaries from ATLAS-CNTY02 were extracted and used to provide the new time zone boundary.

    Data sources used in this process:

    • ATLAS-TZ0506
    • ATLAS-CNTY02
    • CFR-TZ

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    This map layer includes time zones for the United States, Puerto Rico, and the U.S. Virgin Islands.

  5. How consistent are the relationships among the observations, including topology?

    No checks for topological consistency were performed on this map layer.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
None. Acknowledgment of the National Atlas of the United States of America and (or) the U.S. Geological Survey would be appreciated in products derived from these data.

  1. Who distributes the data set? (Distributor 1 of 1)

    Earth Science Information Center, U.S. Geological Survey
    507 National Center
    Reston, VA 20192

    1-888-ASK-USGS (1-888-275-8747) (voice)

    Contact_Instructions:
    In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at <http://geography.usgs.gov/esic/esic_index.html>.
  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey in the use of these data.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 10-Jun-2009
Metadata author:
Terry Higgins
National Atlas of the United States
1400 Independence Rd.
Rolla, MO 65401

573-308-3592 (voice)
atlasmail@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)



 


Generated by mp version 2.9.2 on Wed Jun 10 16:53:51 2009