Storing DateTime (UTC) vs. storing DateTimeOffset

sql

datetimeoffset

datetime

best-practices

byAlex Kataev·Nov 30, 2024

If consistency in one time zone is your key aim, favor DateTime. For capturing the exact instant of an event with a global perspective—which is crucial for apps dealing with multiple timezones—your best bet is DateTimeOffset.

SQL Server example:

-- When you are a 'one timezone' kind of guy/gal
INSERT INTO Events (EventTime) VALUES (GETUTCDATE());

-- When you are a 'global citizen', dealing with multiple time zones
INSERT INTO Events (EventTime) VALUES (SYSDATETIMEOFFSET());

In essence, pick DateTime if you can give the offset a miss; if the offset is important, DateTimeOffset is your friend.

Key Considerations in Choosing DateTime vs DateTimeOffset

This section offers a way to decide whether to use DateTime or DateTimeOffset based on some common cases:

When You're Recording History

DateTime: Sticks to UTC, keeping it simple and consistent.
DateTimeOffset: Overkill, unless you want to record the geographic context of historical events.

For Appointment/Scheduling Systems

DateTime: Requires you to put in extra work for time conversions.
DateTimeOffset: Comes with a built-in local context that's crucial for accurate appointment scheduling.

For User Activity Chronology

DateTime: Offers simplicity but leaves off the context of user local time.
DateTimeOffset: Envelopes the exact moment and the local context of activity, making your logged data richer.

Aggregating Data

DateTime: Forces you to do manual time conversion for data uniformity.
DateTimeOffset: Makes data aggregation easier through standardized UTC alignment with the help of OFFSET.

Bullet Points to Remember

Several factors come into play when deciding whether to use DateTime or DateTimeOffset:

Adapting to the Future

By accommodating daylight savings changes, DateTimeOffset is a step toward future-proofing your application.

Storage Efficiency

When you don’t care about fractions of seconds, DATETIMEOFFSET(0) might be your space-efficient choice, taking up a paltry 8 bytes of storage.

Reporting Simplified

The DATETIME part makes sense for local reports, while OFFSET suits group reports for UTC alignment.

Unpacking it All: Examples and Best Practices

Let's explore some practical examples where DateTimeOffset shines:

Global Flight Ticketing Systems

For handling booking complexities involving multiple time zones, DateTimeOffset comes in handy by maintaining both departure and arrival times in respective local time zones, thus avoiding jet lag... in your database!

Conversions at Database Level

Don't let time conversions bog down your application code. DateTimeOffset brings efficient conversion routines at the database level to the table, resulting in reduced code complexity and better performance.

Compliance with Local Regulations

With DateTimeOffset, aligning with local daylight savings regulations is a breeze. It stores the necessary offset, saving you the troubles of a legal time-travel mess.

Global Interactions Simplified

The offset in DateTimeOffset facilitates easy conversion between time zones, helping you manage global interactions with less hassle. It's like having a world clock in your pocket... or rather your database!

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