When designing a database in SQL Server, one of the common questions that arises is which data type to use for storing date and time values. SQL Server offers multiple data types for this purpose, but two of the most commonly used ones are DATETIME and TIMESTAMP. In this article, we will explore the differences between these two data types and discuss when to use each of them.

Range

The first factor to consider when choosing between DATETIME and TIMESTAMP is the supported range of values. The DATETIME data type in SQL Server can store dates ranging from ‘1753-01-01 00:00:00’ to ‘9999-12-31 23:59:59’. On the other hand, the TIMESTAMP data type has a smaller range, supporting dates from ‘1970-01-01 00:00:01’ UTC to ‘2038-01-19 03:14:07’ UTC.

This means that if you need to store dates that are before the year 1970 or after the year 2038, you will need to use the DATETIME data type. However, if your application’s date range falls within the supported range of the TIMESTAMP data type, you can consider using it.

Conversion

The second factor to consider is the conversion behavior of the data types. In SQL Server, TIMESTAMP values are converted from the current time zone to UTC for storage, and then converted back from UTC to the current time zone for retrieval. This ensures that the timestamp remains consistent regardless of the time zone changes.

On the other hand, DATETIME values are not automatically converted to UTC. They are stored as the exact value provided and retrieved as is. This means that if your application requires the time to be steady with respect to GMT, you should use the TIMESTAMP data type. However, if your application is timezone-dependent and you need to store and retrieve dates based on local time, the DATETIME data type would be more suitable.

Summary

In summary, the choice between DATETIME and TIMESTAMP in SQL Server depends on your specific requirements. If you need a higher range of dates or if your application is timezone-dependent, the DATETIME data type is the better option. On the other hand, if your application is timezone-independent and you want to ensure consistent timestamps regardless of time zone changes, the TIMESTAMP data type should be used.

By understanding the differences between these two data types, you can make an informed decision when designing your SQL Server database and ensure that your date and time values are stored and retrieved accurately.