<aside> ✅ Hit the Copy button in the upper-right corner of this code block. The formula can then be pasted in a Formula property.

</aside>

if(empty(prop("Due")), timestamp(dateAdd(now(), 100, "years")), timestamp(prop("Due")))

Expanded

<aside> ✅ This expanded version of the formula is just for reference and learning.

</aside>

=if(
  empty(
    prop(
      "Due"
    )
  ),
  timestamp(
    dateAdd(
      now(

      ),
      100,
      "years"
    )
  ),
  timestamp(
    prop(
      "Due"
    )
  )
)