Time Zones of the United States

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   National Atlas of the United States, 200506, Time Zones of the United States: National Atlas of the United States, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html>

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: 2005

   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)

   Value	Definition
   Polygon	2-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:	305.704

   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:	2836

   Timezone

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

   Value	Definition
   Alaska	The 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.
   Atlantic	The 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.
   Central	The 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.
   Eastern	The 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-Aleutian	The 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.
   Mountain	The 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.
   Pacific	The 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)

   Value	Definition
   no	Daylight 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)

   Value	Definition
   AL	Alaska time zone.
   AT	Atlantic time zone.
   CE	Central time zone.
   EA	Eastern time zone.
   EAno	Eastern time zone; daylight saving time not observed.
   HA	Hawaii-Aleutian time zone.
   HAno	Hawaii-Aleutian time zone; daylight saving time not observed.
   MO	Mountain time zone.
   MOno	Mountain time zone; daylight saving time not observed.
   PA	Pacific 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?
   Greg Manuel
   National Atlas of the United States
   12201 Sunrise Valley Drive
   Reston, VA 20192
   

   703-648-6433 (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 20)

   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:

   • <http://www.gpoaccess.gov/cfr/index.html>

   Type_of_Source_Media: Online

   Source_Contribution: Spatial and attribute information

   NWS-CNTY (source 2 of 20)

   Service, National Weather , 1999, Counties of the U.S.: National Weather Service, Silver Spring, MD.

   Online Links:

   • <http://www.nws.noaa.gov/geodata/catalog/county/html/county100k.htm>

   Type_of_Source_Media: Online

   Source_Contribution: Spatial and attribute information

   ATLAS-CNTY (source 3 of 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   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 20)

   National Institute of Standards and Technology, Unknown, Time and Frequency from A to Z: National Institute of Standards Technology, Boulder, CO.

   Online Links:

   • <http://www.boulder.nist.gov/timefreq/general/enc-d.htm>

   Type_of_Source_Media: Online

   Source_Scale_Denominator: 2000000

   Source_Contribution: Attibute information

   ATLAS-FEDLAND (source 18 of 20)

   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 20)

   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 20)

   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

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

   Date: 10-Jan-2000 (process 1 of 6)

   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 6)

   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 6)

   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 6)

   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 6)

   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 6)

   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

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?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://nationalatlas.gov/atlasftp.html>

     Data format:	SDTS
     Network links:	<http://nationalatlas.gov/atlasftp.html>

   • Cost to order the data: There is no charge for the map layer.

Who wrote the metadata?

Dates:

Last modified: 16-Jun-2005

Metadata author:

Peg Rawson
National Atlas of the United States
12201 Sunrise Valley Drive
Reston, VA 20192

703-648-4183 (voice)
atlasmail@usgs.gov

Metadata standard:

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