SQL Server Datetime Formats: A Comprehensive Guide

Introduction

Working with date and time values is a routine part of database development. Whether you’re filtering rows, creating reports, or presenting timestamps, consistent formatting helps ensure clarity. This article explains how to format and manipulate dates in SQL Server using built-in tools and functions.

Understanding how to use SQL Server’s datetime functions improves report accuracy, ensures correct regional formatting, and simplifies downstream application logic. In the following sections, we’ll explore the core data types, formatting options, and best practices for datetime in SQL Server.

Data Compliance Overview | Regulatory Frameworks

Handling Time Zones and Quick Style-Code Cheat Sheet

Instant Conversion with AT TIME ZONE

From SQL Server 2016 onward, AT TIME ZONE simplifies converting UTC timestamps into local times (and vice versa) without hard-coding offsets or wrestling with daylight-saving changes.

-- Store once in UTC, present it locally
DECLARE @utc DATETIME2 = SYSUTCDATETIME();

SELECT 
  @utc                         AS StoredUTC,
  @utc AT TIME ZONE 'UTC'
       AT TIME ZONE 'Central European Standard Time' AS BerlinTime,
  @utc AT TIME ZONE 'UTC'
       AT TIME ZONE 'Pacific Standard Time'          AS SeattleTime;

Most-Used CONVERT Style Codes

Stick to ISO styles (120/121) for APIs, reserve locale-specific formats for presentation layers, and always store in UTC when rows travel across regions.

What Is SQL Server?

Microsoft SQL Server is a relational database platform used widely across enterprise environments. It supports transactional and analytical workloads, offering strong capabilities for managing structured data—including built-in tools for datetime storage, formatting, and arithmetic.

SQL Server Date and Time Data Types

SQL Server offers several built-in types for storing and working with datetime values. Some are legacy-compatible, while others offer modern precision and timezone support. Choosing the right type depends on the level of accuracy and storage efficiency you need.

Default Output Format

By default, a query like SELECT GETDATE(); returns a result in the format 'YYYY-MM-DD HH:MI:SS.mmm'. For example:

2024-07-15 13:25:42.347

To customize the format, use the CONVERT() or FORMAT() functions with style codes.

Formatting Dates in SQL Server

Transforming datetime values into readable strings is essential for reports or UI output. The CONVERT() function accepts style codes for various region-specific formats.

DECLARE @date DATETIME = GETDATE();
SELECT 
  CONVERT(VARCHAR, @date, 101) AS US_Format,       -- MM/DD/YYYY
  CONVERT(VARCHAR, @date, 103) AS UK_Format,       -- DD/MM/YYYY
  CONVERT(VARCHAR, @date, 120) AS ISO_Format;      -- YYYY-MM-DD HH:MI:SS

Working with Strings and Dates

When input is received as a string, you can convert it using CONVERT() or CAST() functions. This helps with integration pipelines and dynamic SQL.

DECLARE @str VARCHAR(20) = '2024-07-12 14:30:00';
SELECT CONVERT(DATETIME, @str) AS ConvertedDate;

Whenever precision matters, use datetime2 or datetimeoffset for expanded range and time zone features.

Date Arithmetic

Adding or subtracting time intervals can be handled using DATEADD(). This makes it easy to calculate expiration dates, due times, or reporting windows.

DECLARE @start DATETIME = '2024-07-12';
SELECT
  DATEADD(DAY, 5, @start) AS PlusFiveDays,
  DATEADD(MONTH, 1, @start) AS NextMonth;

Extracting Date Parts

Need a specific part of a datetime? SQL Server offers direct functions to extract year, month, weekday, and more.

SELECT 
  YEAR(GETDATE()) AS Year,
  MONTH(GETDATE()) AS Month,
  DAY(GETDATE()) AS Day,
  DATEPART(WEEKDAY, GETDATE()) AS Weekday;

Best Practices for SQL Server Datetime

1. Use the smallest datetime type that meets your needs. For example, use date if time is irrelevant.
2. Stick to ISO-formatted strings when importing/exporting to avoid ambiguity.
3. Refer to official Microsoft style codes for formatting consistency.
4. Be aware of server locale and language settings—they can alter input parsing and day-month order.

Handling Time Zones

Time zone awareness is critical for global applications. SQL Server’s datetimeoffset helps ensure consistency when storing UTC and converting to local zones.

DECLARE @utc DATETIMEOFFSET = '2024-07-12 12:00:00 +00:00';
DECLARE @cet DATETIMEOFFSET = '2024-07-12 14:00:00 +02:00';
SELECT DATEDIFF(HOUR, @utc, @cet) AS HourDifference;

Summary and Conclusion

Managing and formatting datetime values in SQL Server doesn’t need to be complex. By understanding the right data types and applying conversion functions strategically, you can ensure your applications present time-based information clearly and consistently.

Whether you’re building reports, parsing strings, or implementing time-aware business logic, mastering SQL Server datetime gives you precise control over temporal data. Use built-in functions, follow formatting standards, and leverage timezone support to reduce bugs and improve user trust.