I can use this equation: if (field("fieldname") >= today(), true, false) -- where the field name is a custom date field in an Epic layout, as a calculated column but it won't work as a custom worksheet field equation because have to give the field a type and there is no today() function.
Also it would be nice to be able to add that equation as a calculated column without needing the field to be a column in the list report -- which is how the custom worksheet field seems to work -- I can select any field from the Epic layout.
So these two capabilities are inconsistent and neither of them meets the need completely