You were charging the phone while it was off, right?
Sorry to tell you this, but your phone has a problem in the hardware. It's
not a software bug that resets the date and time of your phone. It's nothing
related to the firmware.
There seems to be a huge quantity of 6230's with this problem. I personally
think that probably ALL the first 6230's had this hardware fault. Many of
the phones which work (or perhaps all, and mine is one of these) bear clear
signs of post-production repair, probably under secret Nokia instructions I
think, into laboratories which were not sufficiently "professional" to do
the job without leaving traces. Then the repaired phones were sold in the
shops.
I am convinced that you, like many others, are one of those whose phone were
not "intercepted" for repair before being sold, so I stongly suggest you go
to the nearest Nokia service centre and get your phone serviced. Nokia
should know very well of this problem, although I doubt it will admit it.
P.S.: It seems that the 6230's are very hard to find in the shops... don't
you smell something? Just to think badly... could it be that they were are
recalled for being serviced even before being distributed?
P.S.2.: You can find a very interesting article about this subject here:
http://www.mobile-review.com/article...a6230-en.shtml