@ctredinnick will be able to help with this :)

Why not use instead:

COMMENT ON SCHEMA "my schema" IS LOCALTIMESTAMP(0); 

Or if really want the current datetime truncated to current minute

COMMENT ON SCHEMA "my schema" IS DATE_TRUNC(‘minute’,LOCALTIMESTAMP()); 

COMMENT ON SCHEMA "my schema" IS LOCALTIMESTAMP(0); 

Or if really want the current datetime truncated to current minute

COMMENT ON SCHEMA "my schema" IS DATE_TRUNC(‘minute’,LOCALTIMESTAMP()); 

I tried both examples (and other similar examples)
postgres throw an error using anything other than pure strings when setting commets. Thats why i need to use FME functions to inject the string directly into the SQL.

 syntax error at or near "DATE_TRUNC"

Hmmm, been years since had a PostGreSQL instance to design on.

Alright well this is a hack to create a dynamic string literal using FORMAT() and give a value formatted to a string literal with the %L format flag.

FME_SQL_DELIMITER ;

DO $$                      
BEGIN
    EXECUTE FORMAT('COMMENT ON SCHEMA “my schema” IS %L', TO_CHAR(CURRENT_TIMESTAMP, 'YYYY-MM-DD HH:MM'));
END $$ LANGUAGE PLPGSQL;

FME_SQL_DELIMITER ;

DO $$                      
BEGIN
    EXECUTE FORMAT('COMMENT ON SCHEMA “my schema” IS %L', TO_CHAR(CURRENT_TIMESTAMP, 'YYYY-MM-DD HH:MM'));
END $$ LANGUAGE PLPGSQL;

Thanks that worked! Thank you for the help :)