> I *could* (I would really like to implement that since it would
> save a lot of work) - but what value crystal would I need for
> this?

What Olin has suggested would be fine

> Or what value is commonly used I should say...

> or a clock rate of 262.144 KHz. I could be wrong in this calculation,
> but doesn't that seem a bit slow??

Not as slow as 32768 !! 262144 (h4000) crystals are available
but I doubt if they are as cheap as the much more common 32k
(which BTW can be scavenged for nothing from all sorts of scrap
boards)

If you check the specs you'll find that power consumption goes down
as frequency and Vcc are reduced, which is what you want for
presumably a 32kHz, battery-operated clock. If you have a mains PSU
then mains cycles would be preferable as the defaut time base and
keep the crystal as back-up when necessary

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics