Here's a glitch I found some time ago with the clock on the TI-84 Plus CE. I've tested this, and reproduced it multiple times, on a revision Pre-A and revision M (faster flash chip) calculator. This issue has been present since at least OS 5.3.0. I have not had a chance to try it on OS 5.6, though.

There are no permanent effects I have seen; that said, I am not responsible for anything bad that happens to your calculator as a result of following the steps below.

1. Set date to 12/31/2132 and time to 11:59 PM
2. Keep your cursor on the Set Clock item in the [MODE] menu.
3. Wait until the clock rolls over to 01/01/33, then immediately hit [ENTER] followed by [GRAPH]. If you time it right, this will cause a domain error; choose Goto in the menu.
4. Your cursor should now be on the day option. Press [2nd][quit]. This will cause a domain error; choose Goto again.
5. The calculator will crash and display garbage on the screen.

On a Revision Pre-A calculator: Reset RAM to fix.
On a Revision M calculator: The calculator will reset itself after some time and verify the OS, but when it reboots it will still be glitched. To get it back to normal, reset the RAM.

My guess is that this glitch causes the calculator to execute from a memory location where it shouldn't be executing.

Hope you find this interesting!
Oh, and here are the details of the calculators I've tested this on:

Revision Pre-A, date code 0315
BOOT version 5.0
Tested on OS 5.3.0, 5.3.1, and 5.4.0

Revision M, date code 0719
BOOT version 5.3.6
Tested on OS 5.3.6, 5.4.0
This seems to reliably reproduce it on N/5.4.0:

1. Reset the calculator
2. In the mode screen, set the time to 2132-12-31 11:59 PM (with M/D/Y & 12-hour mode) & save it
3. Do setTime(23,59,55 at the home screen
4. Quickly return to mode & use the up arrow to get to "SET CLOCK" (before the date rolls over)
5. Wait for the date to roll over, plus a few seconds
6. Press enter
7. Wait for the next screen to finish rendering, plus a few seconds
8. Press graph, etc.

If the graph displays on step 8, you can just set the date again, but I had it work multiple times on the first try. In particular, the exact length of "a few seconds" seems not to be critical. But maybe it depends on something in RAM that varies between attempts.
I could not reproduce on OS 5.6 with my Pre-A on BOOT 5.0.0. However, OS 5.4.0 happily reproduced it on my Rev-M with BOOT 5.3.6!
I just updated to OS 5.6. EDIT: downgraded back to 5.3.0.

The clock now lets you enter dates up to 12/31/9998 (but not 9999). When the date rolls over, the year no longer increments. It just goes back to 1/1/9998.
prime17569 wrote:

The clock now lets you enter dates up to 12/31/9998 (but not 9999). When the date rolls over, the year no longer increments. It just goes back to 1/1/9998.


what if, on older calculators, we used a Hex editor to set the year to 9999? Would it cause interesting effects?
Read this post entirely, because this is weird.

Recently, user Zeroko on the Discord/SAX widget found that this program would stop the RTC chip and cause the day to increment each second: (on OS prior to 5.6, change the year to 2132 instead of 9998)


While 1
Disp getDate

But I also found that it interferes with charging. When this program is run, the charging light blinks once each second as the day increments. Incidentally, when I first discovered the glitch from my first post, I also noticed that the charging light would blink when the clock rolled over.

This could mean that the RTC chip is involved in charging, somehow.

EDIT: Forgot to mention that the above program also breaks the startTmr and Wait commands (possibly more) as well. You will need to set the clock back to the current date if you want to use programs that rely on these.
What is the RTC chip?
(Maybe I should just search for it on the internet, but It's easier if anyone can tell me)
EDIT: I now know what it is.
But I don't think that then does involve charging, I think then it is the same idea as with what I say below
Maybe the blinking of the led is just a sort of 'bussy' indicator then?

About that charging light, that also blinks shortly when I open Cesium (while my calculator is connected to my PC of course) and sometimes also with running some programs.
The TextToMorse program of TheLastMillenial, asmhook, My own board game...
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