Date Calculations in SharePoint List with conditions

mikehamm35, you have probably figured this out already, but:

• If you want an Alert to occur based on days past, the best way to do that is through Power Automate.
• If you want to change the format of your Alpha column, like red if overdue, yellow if 15 days before overdue, etc., then you can use special JSON code to change colors. In the example below, I have formatted for overdue, soon to be due, past due.  The JSON code I used, which I found and modified on one of these extremely helpful forums, is as follows:

{"$schema":"https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json","elmType":"div","attributes":{"class":"= if(Number([$File_x0020_Expires_x0020_On0]) == 0, '' , if([$File_x0020_Expires_x0020_On0] <= @now+86400*15 && [$File_x0020_Expires_x0020_On0] > @now , 'sp-field-severity--warning', if([$File_x0020_Expires_x0020_On0] <= @now, 'sp-field-severity--blocked', if([$File_x0020_Expires_x0020_On0] > @now+86400*75, 'sp-field-severity--good', 'sp-field-severity--good') ) ))"},"children":[{"elmType":"span","style":{"display":"inline-block","padding":"0 4px"},"attributes":{}},{"elmType":"span","txtContent":"@currentField"}]}

This code would go in the Column Formatting field of your calculated column. This is done in SharePoint.

For sending  alerts to people who own the past due content, use a Power Automate flow which looks something like this.

You would change the Get File (properties only) step to Get Items.