SQL Server offers a wide range of data types to store and manipulate datetime values. One of the most advanced datetime data types available is the Datetimeoffset data type, introduced in SQL Server 2008. In this article, we will explore the features and benefits of using the Datetimeoffset data type.

The Datetimeoffset Data Type

The Datetimeoffset data type is designed to store high precision datetime values along with the offset from Coordinated Universal Time (UTC). It is the preferred data type for datetime parameters required by most SQL Server 2008 system functions, such as DATEDIFF and DATEPART.

Let’s take a look at a simple example to understand the components of the Datetimeoffset data type:

DECLARE @utcDatetime datetimeoffset
DECLARE @nycDatetime datetimeoffset

SET @utcDatetime = CAST('2011-03-01 05:00:00 +00:00' AS datetimeoffset)
SET @nycDatetime = CAST('2011-03-01 05:00:00 -05:00' AS datetimeoffset)

SELECT @utcDatetime, @nycDatetime

In the above example, the first variable represents a datetime value in UTC with a timezone offset of zero. The second variable represents a datetime value in New York City with a timezone offset of -05:00 (five hours behind UTC).

When deciding which datetime data type to use, consider the following logical rules:

• Datetimeoffset: Use when the data needs to refer to an exact point in time, such as transaction or updated datetimes (in UTC) and localized datetimes.
• Datetime: Use when the time is irrelevant across time zones or the timezone is unknown, such as imported data or standard datetimes that are the same across timezones.
• Datetime with a 00:00:00 time: Use to represent whole dates, such as dates of birth.
• Time: Use when only the time of the day is relevant and the date is irrelevant, such as opening hours.

Benefits of the Datetimeoffset Data Type

The Datetimeoffset data type offers several benefits:

• Validation of UTC Datetimes: With the Datetimeoffset data type, you can validate that a datetime being passed in is actually in UTC. This ensures data integrity and avoids assumptions.
• Comparison across Timezones: The Datetimeoffset data type allows for easy comparison of datetime values across different timezones. System functions like DATEDIFF can directly work with Datetimeoffset values, eliminating the need for additional variables or function calls.
• Improved Performance: Since most SQL Server 2008 system functions accept Datetimeoffset values as date parameters, using this data type can result in faster processing and improved performance.

Conclusion

The Datetimeoffset data type in SQL Server is a powerful tool for working with datetime values. Its ability to store high precision datetime values along with the offset from UTC makes it a preferred choice for many developers. By using the Datetimeoffset data type, you can ensure data integrity, simplify datetime comparisons across timezones, and improve performance.

If you haven’t explored the Datetimeoffset data type yet, I encourage you to give it a try. It can greatly enhance your datetime handling capabilities in SQL Server.