How to format a cell with data YYYYMMDD in Numbers to be a date type?

I created a custom format to try and format a date column to be used within categories. However, Numbers tend to keep reverting my custom format to "Automatic" and I'm unable to group the data as part of a category.

How do I set cells to use my custom date format to be used in categories?

Setting the field to use the new format

Click away from the cell and go back to the field and see that the format has reverted back to "Automatic"

Solution 1:

You can assign you custom format to an empty cell. If you then enter a value that contains a hyphen (-) or a slash (/), such as "1/21/2019", Numbers assumes it’s a date and assigns it your custom date and time format automatically. And keeps it.

Otherwise, if you already have a number in a cell or enter value that is a number, such as "20171214", Numbers cannot recognize it as a date and assign it your custom date format.

Hope, this little video may help to understand as well: https://youtu.be/fUwRHtRLaec