Date calculation on SharePoint lists between today and a birthdate

jensjakobsen1966 there are a couple of ways to do this. One is with a flow in Power Automate that runs once a day and does the calculation. Another is to have a number column and format it with JSON as follows:

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
  "elmType": "div",
  "txtContent": "=floor((Number(@now)-Number([$Birthday]))/(1000*60*60*24*12)/365*12)"
}

The result is:

Rob
Los Gallardos
Intranet, SharePoint and Power Platform Manager (and classic 1967 Morris Traveller driver)