hmm, are you sure that ntpdate has been superseded by rdate? As far as I know it's the other way around: rdate has been replaced by ntpdate.

The reason being that rdate changes the date/time immediately, whereas ntpdate will drift the clock gently until the correct date/time has been reached (for a delta t not too large), in order to not break some software that doesn't like having the time change abruptly.