Understanding the DateTime Encoding in SQLite for Delphi Applications

Learn how to convert SQLite `datetime` values into Delphi `TDateTime` format with our easy guide.
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Understanding the DateTime Encoding in SQLite for Delphi Applications

When working with databases, especially when integrating data from different systems, issues can arise regarding data formats and encodings. A common challenge faced by developers is manipulating datetime values correctly. In this post, we will discuss a specific scenario encountered by a Delphi developer who needed to read datetime values stored in an SQLite database and convert them into a usable format. Let’s dive into this problem and explore how to resolve it effectively.

The Problem: Converting SQLite datetime Values in Delphi

In the scenario presented, a Delphi developer was unable to retrieve and convert datetime values stored in an SQLite database due to a misunderstanding of how datetime values are stored and represented. Here’s a summary of the situation:

The data in column 3 of the database represents datetime values stored as integers, which actually indicate the number of 100-nanosecond intervals since January 1, 0001.

The developer's program was displaying datetime values in a human-readable format in column 2, but there was difficulty in converting the stored integer values back into this format.

Here are a few rows of the data causing confusion:

[[See Video to Reveal this Text or Code Snippet]]

The central question is: How do you translate the integer value in column 3 into a readable datetime value?

The Solution: Conversion to Delphi's TDateTime

To accurately convert the datetime values stored in the SQLite database into a TDateTime value that Delphi can understand, you can follow a straightforward calculation. The key is recognizing that the stored value is in the format of hundreds of nanoseconds since a defined epoch.

Conversion Formula

You can utilize the following formula within your Delphi program:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Formula

Value: This is the integer that you read from the SQLite database (e.g., the value from column 3).

864000000000: This constant represents the number of 100-nanosecond intervals in one day (there are 86400 seconds in a day, and each second has 10 million 100-nanosecond intervals).

693593: This number is the date offset necessary for adjusting the result into Delphi's TDateTime format because Delphi's TDateTime starts counting from 30 December 1899.

Example Calculation

Let’s walk through an example using the first integer value from the database:

Extract the value: 621939168000000000

Apply the formula:

[[See Video to Reveal this Text or Code Snippet]]

Calculate:

First, perform the division: 621939168000000000 / 864000000000 = 720812.500000 (This gives days since the base date).

Then subtract 693593:

So, 720812.500000 - 693593 = 27119.500000.

This result corresponds to 11/7/1971, which is the datetime value initially presented in column 2.

Conclusion

Successfully converting datetime values stored in an SQLite database to a format that Delphi can use requires an understanding of how those values are represented. By applying the conversion formula outlined above, you can ensure that your Delphi application accurately reflects human-readable dates and times.

If you encounter similar issues or have additional questions on datetime handling with Delphi, feel free to reach out or leave a comment below. Happy coding!