Instead of using a very long set of If statements, I think you could just use something like

    a=$((`date +%M`/15));b=$((128335 + `date +%l` +((a*(a**2-39*a+110))/6)));printf '%x' $b;

and print the resulting hex's character, no?

(I'd finish off the code myself, but I have a bus to catch)

Edit: Ah, I see Sephr came prepared. ;)