Any advice on how to solve the "syntex/missing operator" error message the below calculated field is returning? In short, I need to calculate tenure: so if no termination date, then use today and if no Seniority Date, then use Hire Date

Calculated field currently looks like this:

DATEDIFF('year', IFNULL([Termination date], TODAY()),

DATEDIFF('year', IFNULL([Enterprise Seniority date], [Hire Date])))