You can use conditional formatting in Excel to highlight cells containing dates older than or younger than a certain date. Here's how:

1. Select the cells you want to format.

2. Apply Conditional Formatting:

* Go to the Home tab.
* Click on Conditional Formatting.
* A dropdown menu will appear.

3. Highlight Based on Rules:

There are two main approaches depending on your need:

* Highlight cells older than a certain date:
* Choose Highlight Cells Rules > Less Than...
* Highlight cells younger than a certain date:
* Choose Highlight Cells Rules > Greater Than...

4. Set the comparison date:

In the following prompt "Format cells that are...", enter the date you want to compare against. You can:

* Type the date directly: For example, enter `10/07/2024` (adjust the format based on your region).
* Reference a cell containing the date: Click on the cell reference box and select the cell where you have the comparison date entered.

5. Choose formatting (Optional):

Click on the Format button to customize how you want to highlight the cells that meet the criteria. You can change the fill color, font color, or other formatting options.

6. Click OK.

Excel will now apply the conditional formatting to your selected cells. Any cell containing a date older than (or younger than) the specified date will be highlighted according to your chosen formatting.

Tips:

* You can use similar logic with other comparison operators like "Equal To," "Not Equal To," "Between," etc., depending on your specific needs.
* To highlight cells based on today's date, you can use the formula `=TODAY()` in the comparison date field.