The standard A1200 had provision for an internal clock via a secret
bit of removeable shielding which concealed a little row of pins (the
clockport). An internal clock could be added without needing an
accelerator or memory card. Incidentally this `clock port' has the
capacity for incredible speed and in the latter nineties was used for
300kbps serial ports etc.
Can't say I've ever seen a clockport clock, all I ever saw was that
little grey and red parallel port clock. Or was it the DF1: passthru?
The Blizzard accelerators have a self-recharge Panasonic CR2020. It
recharges when the Amiga is on, keeps the clock ticking when the Amiga
is off. I know these little self-recharge buttons can keep the data in
a PDA/Console for at least a month, so could probably keep the time
for ages on your Amiga.
Remember, if ever one of these dies it'd be best to replace it with
another Panasonic CR2020. If you get a socket and put non-recharge
ones in you'll be paying 2.50 UKP every few months, and it'll probably
leak and blow up (unless you put a diode in to cut the recharge line
of the Blizzard).
Also, is this the coolest CLI utility ever?
http://ftp.uni-paderborn.de/pub/aminet/util/cli/cal20.lha