Alpine 9855 and 9853 Head Unit Question Re: Clock

I am replacing my stock Mach 460 head unin my 2000 GT with either an Alpine 9855 or a 9853 head unit. I am wondering if the the new head unit will have a clock that is always on like the stock head unit, or if it will only show when the head unit is powered on. That is, if I am driving and I do not have the stereo on, does the clock still show the time, or will it only show when I have the deck turned on. I have never had an Alpine hu so I am not familiar with them.

Thanks for any help to be offered.

~Darren