IANA Time Zone Support for Microsoft SQL Server
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README.md

SQL Server Time Zone Support

This project adds full support for time zones to Microsoft SQL Server.

This implementation uses the industry standard IANA time zone database. If you are used to Microsoft Windows time zones, such as used with .NET TimeZoneInfo, consider using IANA time zones by using the Noda Time library.

You can read more about the IANA time zone database on Wikipedia, and on StackOverflow.

A list of supported time zones can be found here.

Note: This is an un-official, personal project. It is not developed or supported by Microsoft.

News:

SQL Server 2016 includes built-in support for Windows time zones using a new AT TIME ZONE syntax. If you only need support for Windows time zones (not IANA time zones), consider using this feature instead of this project. Read the news here, and documentation here.

Installation

  1. Download the latest sqltz.zip file from the releases page.

  2. Extract the zip file to a directory.

  3. Open the tzdb.sql file, and run it against your database.

    • It will create all objects in an independent schema called [Tzdb].
    • Microsoft SQL Server 2008 R2 and higher are supported, including Azure SQL Database.
  4. Run the SqlTzLoader.exe utility, passing the connection string with the -c parameter.
    For example:

    SqlTzLoader.exe -c"Server=YourServerName;Database=YourDatabaseName;Trusted_Connection=True"

    or

    SqlTzLoader.exe -c"Server=YourServerName;Database=YourDatabaseName;User Id=foo;Password=bar"

    It will download the latest time zone data and populate the tables in the database.

Staying Current

You can re-execute the SqlTzLoader.exe utility any time. If new time zone data is available, it will download it and update the tables. You can easily run this from SQL Agent, Windows Scheduler, or Azure Scheduler. Please do not run it more than once daily.

Our data comes from the Noda Time TZDB NZD files, which in turn is generated directly from IANA releases. Therefore, you may notice a short delay between publishing of IANA TZDB and the updated NZD file being made available.

Usage

There are several user-defined functions exposed for common time zone conversion operations. If you need additional functions, please create an issue in the issue tracker.

UtcToLocal

Converts a datetime or datetime2 value from UTC to a specific time zone. The output is a datetimeoffset value that has the correct local time and offset for the time zone requested.

-- SYNTAX
Tzdb.UtcToLocal([utc_datetime], [dest_timezone])

-- EXAMPLE
SELECT Tzdb.UtcToLocal('2015-07-01 00:00:00', 'America/Los_Angeles')
-- output: '2015-06-30 17:00:00 -07:00'

LocalToUtc

Converts a datetime or datetime2 value from a specific time zone to UTC. The output is a datetimeoffset value that has the correct UTC time and an offset of +00:00.

Be aware that local-to-utc conversion is potentially a lossy operation. For more details, consult the dst tag wiki on StackOverflow.

-- SYNTAX
Tzdb.LocalToUtc([source_datetime], [source_timezone], [SkipOnSpringForwardGap], [FirstOnFallBackOverlap])

-- EXAMPLE
SELECT Tzdb.LocalToUtc('2015-07-01 00:00:00', 'America/Los_Angeles', 1, 1)
-- output: '2015-07-01 07:00:00 +00:00'
  • The SkipOnSpringForwardGap parameter has the following options:

    • 1 : If a local time is in a DST gap due to the "spring-forward" DST transition, it is assumed that the clock should have sprung forward but didn't. It therefore advances the time by the DST bias (usually 1 hour) so it can return a valid UTC time. This is the default option.
    • 0 : If a local time is in a DST gap due to the "spring-forward" DST transition, the function returns NULL.
  • The FirstOnFallBackOverlap parameter has the following options:

    • 1 : If a local time is ambiguous due to the "fall-back" DST transition, the first occurrence is assumed. This will always be the daylight time instance. This is the default option.
    • 0 : If a local time is ambiguous due to the "fall-back" DST transition, the second occurrence is assumed. This will always be the standard time instance.

ConvertZone

Converts a datetime or datetime2 value from a specific time zone to another specific time zone. The output is a datetimeoffset value that has the correct local time and offset for the destination time zone requested.

The DST option flags are the same as the LocalToUtc function, and apply to the source time zone only.

-- SYNTAX
Tzdb.ConvertZone([source_datetime], [source_timezone], [dest_timezone], [SkipOnSpringForwardGap], [FirstOnFallBackOverlap])

-- EXAMPLE
SELECT Tzdb.ConvertZone('2015-07-01 00:00:00', 'America/Los_Angeles', 'Australia/Sydney', 1, 1)
-- output: '2015-07-01 17:00:00 +10:00'

SwitchZone

Converts a datetimeoffset value to a specific time zone. The output is a datetimeoffset value that has the correct local time and offset for the time zone requested.

This function is similar to SQL Server's SWITCHOFFSET function, however it accepts a time zone instead of an offset - so it can take daylight saving time into account.

-- SYNTAX
Tzdb.SwitchZone([source_datetimeoffset], [dest_timezone])

-- EXAMPLE
SELECT Tzdb.SwitchZone('2015-07-01 00:00:00 -04:00', 'Asia/Kolkata')
-- output: '2015-07-01 09:30:00 +05:30'

GetZoneAbbreviation

Determines the correct abbreviation to use for the datetimeoffset value and time zone provided. The output is a varchar(10) containing the abbreviation requested.

If you don't have a datetimeoffset, you should first obtain one either by using the LocalToUtc or UtcToLocal conversion functions, or by crafting it manually with SQL Server's TODATETIMEOFFSET function. Do not pass a datetime or datetime2 in, or the server's local time zone will get applied during the conversion.

Note that the abbreviations for many time zones depend on the specific date and time that they apply to.

-- SYNTAX
Tzdb.GetZoneAbbreviation([datetimeoffset], [timezone])

-- EXAMPLE
SELECT Tzdb.GetZoneAbbreviation('2015-07-01 00:00:00 -04:00', 'America/New_York')
-- output: 'EDT'

Shameless Plug

If you want to learn more about time zones, and all of the lovely bits of programming that go around them, please consider watching my Pluralsight course, Date and Time Fundamentals.

I also have a blog at CodeOfMatt.com, which covers several issues surrounding dates, times, and time zones.

Thanks!

License

This project is made freely available under the MIT license. Attribution is requested.

This project uses the following external resources: