CD 4051 (MUX / DEMUX) circuit

Download and install Swordfish BASIC SE. I have a one page tutorial in my blueroomelectronics Junebug manual (google it). Swordfish is an excellent modular & modern BASIC compiler.

You need a PICKit2 or 3.

You could make the PIC itself the battery backed up RTCC, Timer1 supports a 32,768kHz watch crystal and this can wake the PIC on overflow from very low power sleep to update the clock. The 18F4620 has a built in low power detector that could switch off a display when power is lost. The simple resistor / diodes / supercap schematic posted earlier should do the trick. Then it's all about learning the software.

The simplest possible LED clock would be 1H:MM where the 1 is either off or 1
Pincount for the display
1 - 1
7 - H
1 - seperator (flashing dots, optional)
7 - M
7 - M
so 23 pins for the display
2 - switches for setting the time
2 - 32768kHz crystal + 22pF caps
3 - In circuit programming ie PICkit (optional)

total 30 I/O pins.
You'll need 470 ohm resistors for each display segment and some filter + decoupling caps.

I've never used basic on pics, the 16f628 is a popular chip, the 16f88 is also a good choice for one with a/d.
You might be better off with something a little more powerfull for running basic like blooroom suggested.
Pickit 3's in this country are only around 30 quid and are not difficult to use.

Hi, I have ordered a PicKit2 starter set from Microchip. I shall be experimenting a bit before I start on a clock. Whilst there are ready made ccts and programs to make a clock and of course there are only so many ways to make a clock . I really would love to "invent" my own. Or at least put my own "stamp" on the cct.
Thanks for all your help. I am sure I'll be back with questions about the pics.

A simple single led flasher is a good project to start with, on say a pic16f628, if you can do that you can understand the nut and bolts.
There is a section of code in the datasheet for the '628 that shows how to perform a real time clock in software with a 32kc xtal in conjuntion with timer1, I've used it a few times and its accurate.