Auto Populate

When your user selects a value for the 'last-updated' date you can add, on that same date field component, an a!save() to save the derived value of last-upadate+2years into the variable that you are using as the value attribute of your 'next-update' field. Assuming you don't want your user to override the 'next-update' value you should make this read-only and use a different component to display its value (i.e. the underlying variable type will be date but a read-only display of this value should be a text field, where you can use the text() function to render a friendly date, like "Tuesday 25th March 2022")

Here's an example of what I meant:

a!localVariables(
  local!lastUpdated: null,
  local!nextUpdate: null,
  {
    a!dateField(
      label: "Last UHpdated",
      value: local!lastUpdated,
      saveInto: {
        local!lastUpdated,
        a!save(
          local!nextUpdate,
          local!lastUpdated + (365 * 2)
        )
      }
    ),
    a!textField(
      label: "Next Update",
      readOnly: true,
      value: if(
        fn!isnull(local!nextUpdate),
        "",
        fn!text(local!nextUpdate, "ddd mmm yyyy")
      )
    )
  }
)

Here's an example of what I meant:

a!localVariables(
  local!lastUpdated: null,
  local!nextUpdate: null,
  {
    a!dateField(
      label: "Last UHpdated",
      value: local!lastUpdated,
      saveInto: {
        local!lastUpdated,
        a!save(
          local!nextUpdate,
          local!lastUpdated + (365 * 2)
        )
      }
    ),
    a!textField(
      label: "Next Update",
      readOnly: true,
      value: if(
        fn!isnull(local!nextUpdate),
        "",
        fn!text(local!nextUpdate, "ddd mmm yyyy")
      )
    )
  }
)