How to conditionally format a date column that is two weeks old?

StephDH246 

If you want to get the number of milliseconds since 01.01.1970, you need the expression

Number(Date([$Created]))

So if you want to select all Dates before two weeks ago you could use the formula

Number(Date([$Created]))<(Number(Date(@now))-1209600000

 (1209600000 = 14 * 24 * 60 *60 *1000).

You can access other fields in the view. If you have a field "CellToBeEmpty" and that field is in the view, then you can access the value of the field like this : [$CellToBeEmpty]

With two nested "if" statements, your json would look like this

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "style": {
    "box-sizing": "border-box",
    "padding": "0 2px",
    "overflow": "hidden",
    "text-overflow": "ellipsis"
  },
  "attributes": {
    "class": "=if([$CellToBeEmpty],'',if(Number(Date([$Created]))<(Number(Date(@now))-1209600000),'sp-css-backgroundColor-BgRed sp-css-borderColor-CoralFont sp-field-fontSizeSmall sp-css-color-WhiteText',''))"
  },
  "txtContent": "[$Created.displayValue]"
}