GeoTime 1.0.0

.NET 5.0
dotnet add package GeoTime --version 1.0.0
NuGet\Install-Package GeoTime -Version 1.0.0
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package.
<PackageReference Include="GeoTime" Version="1.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add GeoTime --version 1.0.0
#r "nuget: GeoTime, 1.0.0"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install GeoTime as a Cake Addin
#addin nuget:?package=GeoTime&version=1.0.0

// Install GeoTime as a Cake Tool
#tool nuget:?package=GeoTime&version=1.0.0


GitHub .NET CodeQL

GeoTime aims to be a fast, lightweight, and memory-efficient C# library for querying timezone abbreviations.



GIF demonstrating the GeoTime library


Package Manager Console:

PM> Install-Package GeoTime -Version 1.0.0


nuget install GeoTime -Version 1.0.0


dotnet add package GeoTime --version 1.0.0

System requirements


  • TZAbbr: An entity representing an abbreviated timezone, which holds: a unique ID, an abbreviation, a name, and an offset (in seconds).
  • TZAbbrLookup: A high-level service that allows looking up information about abbreviated timezones
  • TZAbbrLookupFactory: A factory for creating instances of a TZAbbrLookup service
  • TZAbbrStore: A low-level service that holds a read-only dictionary, mapping unique primary keys/IDs to abbreviated timezone (IReadOnlyDictionary<int, TZAbbr>)
  • TZAmbiguityStore: A low level indexed service that holds a read-only dictionary, mapping timezone abbreviations to a set of timezone IDs (IReadOnlyDictionary<string, HashSet<int>>)
  • TZAScraper: A service that cleans and indexes the timezones.json into smaller and more usable data.

The concept of ambiguity

We say a timezone abbreviation is ambiguous, if it can possibly stand for multiple different timezones. For example, BST can mean:

Building the timezone data

The original timezone data is auto-extracted from an HTML table using a JS snippet, and then placed into data/timezones.json.

To build the data and make it usable, you can run the GeoTime.Build project, which will produce two files in the /artifacts folder:

  • List file - timezones.list.json: Holds a map which maps a unique primary key/ID to an abbreviated timezone.
  • Ambiguity file - timezones.ambiguity.json: Holds a map which maps the timezone abbreviations (string keys) to the unique ID of a timezone it can stand for (array of integers).

Notes: The following issues are being worked on.

  • The artifacts are not automatically placed into the artifacts folder, and will have to be manually moved from src/GeoTime.Build/bin/Release/net5.0 to artifacts.

Memory and performance

  • The datasets combined (already minified), totals to 20 KB.
    • Compressing into a ZIP will drop it to a total 6.17KB (3.24x smaller).
    • gzipping both files will drop it to a total 5.2KB (3.85x smaller).

Constructing the lookup service will take the most time, as this requires indexing all the timezone data by deserializing two JSON files into C# read-only dictionaries. After creating a lookup, querying for info will generally run under much quicker times.


TZAbbrLookup lookup = new TZAbbrLookupFactory().GetLookup();

Check if an abbreviation is ambiguous

Checking if an abbreviation is ambiguous takes constant time (O(1) time).

lookup.IsAbbrAmbiguous( "CST" ); // true
lookup.IsAbbrAmbiguous( "ART" ); // false

Get an abbreviated timezone by ID or name

Querying an abbreviated timezone by their...

  • ...unique integer ID takes O(1) time.
  • ...unique full name will take linear time (O(n) time), where n represents the number of timezone abbreviations.
TZAbbr novosibirsk = lookup.GetTimeZone( 149 );
// new TZAbbr( 149, "NOVST", "Novosibirsk Summer Time", 25200 )

TZAbbr argentina = lookup.GetTimeZone( "Argentina Time" );
// new TZAbbr( 22, "ART", "Argentina Time", -10800 )

Console.WriteLine( argentina.Abbr ); // "ART"
Console.WriteLine( argentina.OffsetInSeconds ); // -10800
Console.WriteLine( argentina.GetOffset().ToString() ); // "-03"

TZAbbr someTZ = lookup.GetTimeZone( "Foo" );
// throws TimeZoneNotFoundException

Get possible timezones from an abbreviation

Querying a list of timezones by abbreviation will take O(1+n) time, where n represents the number of timezones an abbreviation can possibly stand for. The first operation will be a dictionary lookup, and the n operations after will be dictionary lookups of the timezones by ID.

  • In average case and best case: O(2) (An abbreviation maps to 1 timezone)
  • In worst case: O(4) (An abbreviation maps to 3 timezones)
lookup.GetTimeZonesByAbbr( "CST" );
   new HashSet<TZAbbr>() {
      new TZAbbr( 61, "CST", "Central Standard Time", -21600 ),
      new TZAbbr( 62, "CST", "China Standard Time", 28800 ),
      new TZAbbr( 63, "CST", "Cuba Standard Time", -18000 )

lookup.GetTimeZonesByAbbr( "PGT" );
   new HashSet<TZAbbr>() {
      new TZAbbr( 166, "PGT", "Papua New Guinea Time", 36000 )


GeoTime is licensed under the MIT license.

Product Versions
.NET net5.0 net5.0-windows net6.0 net6.0-android net6.0-ios net6.0-maccatalyst net6.0-macos net6.0-tvos net6.0-windows net7.0 net7.0-android net7.0-ios net7.0-maccatalyst net7.0-macos net7.0-tvos net7.0-windows
Compatible target framework(s)
Additional computed target framework(s)
Learn more about Target Frameworks and .NET Standard.

NuGet packages

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GitHub repositories

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Version Downloads Last updated
1.0.0 267 2/28/2021