Hi, I am not sure if this is an issue or perhaps these features are not implemented yet. But as per the documentation, date expressions are supported.
When I tried a basic date expression :
Expression expr = new Expression("DATEDIF(DATEVALUE('2021-01-31'),DATEVALUE('2029-08-29'),'Y')");
String value = expr.Eval<String>();//The United States of America
Console.WriteLine(value);
I get an exception : System.Exception: Function DATEVALUE does not exist]