Clock-in-a-Menu, by Joe Horn.  Time appears in the CST menu label.

--> S/SX/G/GX

My answer to a recent EduCALC HP 48 Programming Class Challenge.

Include this list IN ITS ENTIRETY as a SINGLE object INSIDE of the
'CST' list, and you'll have a handy clock that doesn't drain the
batteries or cause hiccups, like the status-line clock does.

    CAUTION: Follow the above instruction carefully!  If you use + or
    REPL to place this list into 'CST', it will not work properly.  If
    you are not familiar with list operations and custom menu
    construction, then follow these explicit instructions:

    BEGINNER INSTRUCTIONS:  Load 'CLKMENU' into memory. Press the CST
    key.  If the six softkeys are all blank, then do CLKMENU { } +
    MENU.  Otherwise, do 'CST' CLKMENU 1 ->LIST STO+ and then press
    CST to verify that the "clock menu" softkey has been added to the
    end of your custom menu.

At every display update (e.g. when you press ENTER, or perform a
calculation, or press ON, or CST...), it updates itself automatically
to display the time (HH:MM). Note that it does NOT update when
nothing's happening. So it'll show the correct time as long as you are
actually USING your HP48.  It respects your 12/24-hr time format mode.
It removes leading zeroes because that looks better.

Pressing the key returns the current time & date, including
day-of-week, to the stack.  The day-of-week is in English, to preserve
S/SX compatibility.  ->TIME and ->DATE are assigned to the left and
right shifted versions of the key, respectively, so you can easily
set, view, and recall the time and date, all from one key.

This works okay in rev "R".  It should work in all other versions too,
but of course I guarantee nothing.  It uses one UNSUPPORTED ENTRY
POINT: #D2F0h, which converts a date (real number) into a three-letter
day-of-week string.  This entry point has been stable in all versions
A thru R.

Unanswered Question #782673:  Can the "clock mode" (controlled by flag
-40) be re-vectored to run something other than the ordinary clock-in-
the-status-area routine?  I'd like the system to call my own clock
routine every second.  Can it be done?  (No, I *don't* want to use a
repeating alarm!  That slows down the machine too much.)

-Joe Horn-