DATETIMEOFFSET

DATETIMEOFFSET is a data type in Microsoft SQL Server that stores date and time values along with a time zone offset. This is particularly useful in applications where you need to account for different time zones or when it’s essential to track the time with an offset from UTC. Unlike the standard DATETIME type, which only stores date and time, DATETIMEOFFSET includes information about the offset from UTC, allowing you to handle time zones more effectively.

Syntax and Storage

The syntax for DATETIMEOFFSET is as follows:

DATETIMEOFFSET(fractional_seconds_precision)

fractional_seconds_precision: Defines the number of decimal places for fractions of a second, ranging from 0 to 7. For example, DATETIMEOFFSET(3) stores milliseconds (up to three decimal places).

A DATETIMEOFFSET value is stored in a 10-byte format, with the following breakdown:

8 bytes for the date and time values
2 bytes for the offset

Format of DATETIMEOFFSET

The DATETIMEOFFSET data type follows the format:

YYYY-MM-DD hh:mm:ss[.fractional_seconds] {+|-}hh:mm

For example:

2023-11-12 15:30:00.1234567 -05:00

Here, 2023-11-12 is the date, 15:30:00.1234567 is the time with fractional seconds, and -05:00 is the offset from UTC.

Benefits and Use Cases

Time Zone Handling: DATETIMEOFFSET is ideal for applications that deal with multiple time zones since it stores both the local time and the offset.

Conversion to UTC: It simplifies conversions to UTC because the offset is part of the data. For example, using functions like SWITCHOFFSET and TODATETIMEOFFSET allows you to easily manage UTC and other time zones.

Compatibility with External Systems: Many external systems and APIs require or return data with time zone information, making DATETIMEOFFSET compatible for integrations.

Example

Defining and Storing DATETIMEOFFSET Data

CREATE TABLE Events (
    EventID INT PRIMARY KEY,
    EventName NVARCHAR(50),
    EventDateTime DATETIMEOFFSET(3)
);

INSERT INTO Events (EventID, EventName, EventDateTime)
VALUES (1, 'Webinar', '2024-03-15 14:00:00.000 -07:00');

Converting Between Time Zones You can use SWITCHOFFSET to adjust the time zone offset without changing the UTC time:

SELECT SWITCHOFFSET(EventDateTime, '-05:00') AS EventEasternTime
FROM Events;

Converting to UTC Using the AT TIME ZONE function, you can easily convert DATETIMEOFFSET to UTC:

SELECT EventDateTime AT TIME ZONE 'UTC' AS EventUTC
FROM Events;

Limitations

Increased Storage Size: DATETIMEOFFSET requires 10 bytes, which is larger than DATETIME (8 bytes) or SMALLDATETIME (4 bytes).

Complexity: Handling time zones and offsets can add complexity, especially when data from multiple time zones needs to be compared or calculated.

In summary, DATETIMEOFFSET in SQL Server is a powerful tool for applications that require precise time tracking with time zone information, offering both flexibility and ease of conversion to different time zones.