/* postgres can not */
select Date("2001-01-01") - Datetime("2001-01-01T00:00:00Z");
select Date("2001-01-01") - Timestamp("2001-01-01T00:00:00Z");
select Datetime("2001-01-01T00:00:00Z") - Timestamp("2001-01-01T00:00:00Z");
select Datetime("2001-01-01T00:00:00Z") - Date("2001-01-01");
select Timestamp("2001-01-01T00:00:00Z") - Date("2001-01-01");
select Timestamp("2001-01-01T00:00:00Z") - Datetime("2001-01-01T00:00:00Z");