SQL Server DateTime vs DateTime2

When working with dates and times in SQL Server, you have options to choose from for the data type to store these values. The two commonly used data types are DateTime and DateTime2. In this guide, we will compare these two data types and provide insights to help you choose the appropriate one based on your requirements.

DateTime

DateTime is a data type in SQL Server that stores dates and times from January 1, 1753, to December 31, 9999, with an accuracy of three milliseconds. It has the following format:

YYYY-MM-DD HH:MI:SS

Some key points about DateTime:

• It occupies 8 bytes of storage.
• The time part has a fixed precision of 3.33 milliseconds.
• It has a range of values from January 1, 1753, to December 31, 9999.
• It has a resolution of 0.00333 seconds (equivalent to 3.33 milliseconds).
• It does not store time zone information.

DateTime2

DateTime2 is an enhanced version of the DateTime data type introduced in SQL Server 2008. It offers greater precision and a larger range of values. It has the following format:

YYYY-MM-DD HH:MI:SS[.NNNNNNN]

Some key points about DateTime2:

• It occupies between 6 to 8 bytes of storage, depending on the precision used.
• The precision can be specified up to 7 digits for fractional seconds, allowing more precise time measurements.
• It has a range of values from January 1, 0001, to December 31, 9999.
• The precision can be set at either 0, 1, 3, 4, 5, or 7 digits for fractional seconds.
• It does not store time zone information.

Choosing between DateTime and DateTime2

When deciding between DateTime and DateTime2, consider the following factors:

• Range of Values: If you require a range of values beyond the supported range of DateTime (January 1, 1753 to December 31, 9999), choose DateTime2.
• Precision: If you need high precision for time measurements, such as for scientific simulations or financial calculations, DateTime2 allows you to specify a higher precision for fractional seconds.
• Storage Size: If storage size is a concern, note that DateTime2 has a variable storage size compared to the fixed 8 bytes used by DateTime. Choose DateTime2 only if you require the additional features it offers.

In most cases, it is recommended to use DateTime2 as it offers more flexibility and better precision. However, if you are working with legacy systems or have specific constraints that require the use of DateTime, it can still be a viable option.

Conclusion

In this guide, we discussed the differences between DateTime and DateTime2 data types in SQL Server. We covered their formats, key features, and factors to consider when choosing between them. Make an informed decision based on your specific requirements, and remember that DateTime2 is generally the preferred choice for new projects.