> For the complete documentation index, see [llms.txt](https://kb.logicerp.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kb.logicerp.com/logic-erp-learning-hub-tutorials-and-best-practices/defining-custom-columns-in-reports-and-grids-with-expressions/datediff-function.md).
# DateDiff () Function
**YouTube:** [How to Use the DateDiff () Function in Report Custom Columns?](https://www.youtube.com/watch?v=SXu7wbNw8VU)
## How to Use the DateDiff () Function in Report Custom Columns?
In this tutorial, we’ll learn how to calculate the **difference between two dates** using the `DateDiff` function in a report grid. This is helpful for calculating aging, due periods, or durations between dates.
***
### Accessing the Expression Designer:
* Navigate to the **Reporting** section.
* Open the **Sales Register Detailed Report** or any **"Report".**
* Go to **Setup Column Attributes**.
* Here, you'll see a list of available columns that can be used to build expressions.
* Click on **"Add/Edit Expression Columns"** where you can write your expression using predefined functions.
* Before adding the expression to the report, go to **Other Settings**.
* Ensure the **Script Editor** is set to **VBScript**.
* Click **Save**.
* *Note: VBScript is the default for new configurations but always verify this setting.*
### Writing Your First Expression
* Every expression must start with the script header: **'#@LSCRIPT**
* Click the (+) Plus icon to create a new expression.
* Fill in the required fields:
* **Expression Name** – A unique name for your expression.
* **Expression Type** – Choose either **Text** or **Numeric** depending on the expected output.
### Creating a Simple DateDiff() Expression
* Double-click the new expression name to insert it into the script editor.
* Define the expression using the syntax:
* **Expression Name** = DATEDIFF("D",CDATE(BILL\_DATE),NOW)
* `"D"` → Calculates difference in **days**
* `CDate(BILL_DATE)` → Converts the bill date string to a date
* `Now` → Represents the current system date
**Other interval options:**
* `"M"` – Months
* `"Y"` – Years
* `"D"` – Days (most commonly used)
* Save the expression once defined.
* Scroll down and **check the box** beside the expression name to enable it.
* Save and proceed to check the effect.
* **Refresh the report** to view the final result.
***
### Output:
* If `BILL_DATE = 01/06/2025` and today is `09/06/2025`,\
the column will show: `8`
This expression is widely used in reports like **aging analysis**, **credit control**, and **follow-up tracking**.
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