I need to set the calendar and date on calculator P170-DH. How do I change from AM to PM

press the calendar/clock key (top row, second from the left)
press the "=" key (clock/date set) and hold till display flashes
key in the correct date
press the calendar/clock key
key in the correct time and remember to select AM or PM (#/diamond key)
press the calendar/clock key
CE/E returns to calculator function

Press the Date and Time button on the calculator. It is to the right of the Feed button and has a small calendar and clock on it. To set the date, press the button once to display the factory supplied date and hold down the Equal ( = ) button that is two buttons below Date and Time until the screen flashes. Input the correct date. Ex: August 20, 2010 would be entered on the numerical keyboard of the calculator at 08202010. When finished, hold the Equal button again. Do the same for the time.

To sum it up:

Press Date and Time button
Hold = button until blinks
Enter date or time
Hold = button again until blinking stops

Press the button to the right of the FEED button twice. The first time you press it will be for the Date, the second will bring up the time.

1. Press the calendar/clock button twice
2. Press and hold the Clock/Date Set (or Time Set) button for three seconds.
3. Use the numeric keys to enter the time -- four digits (i.e., 0730)
4. Press the AM/PM button to select
5. Press the Clock/Date Set (or Time Set) button
6. Press the C/CE button to return to calculation mode

CLOCK & CALENDAR FUNCTION

Look for the key with the cal/clock pic on it. Use to switch between calendar or clock mode. It is next to the feed key.
(12/24) Key used to switch between 12 or 24 hour at clock mode.
(Time Set) Key used to set the date and time in calendar & clock mode.
(AM/PM) Key used to switch between AM or PM at clock mode time setting.
(Format) Key used to select date format between "YYYY/MM/DD",
"DD/MM/YYYY" or "MM/DD/YYYY" at calendar mode.
Hope this helps, play with it I figured it out with instruction sheet.

for calandar
turn on.
press clock calandar button, top row second from left.
press time set button, second row from left, 3rd button from top, (has time set printed diretly above)
enter numbers, say 03 05 2009
press time set button 3 seconds
press CE/E, red key at bottom left corner.

turn on
press clock calandar button once, date will show
press clock calandar button 2nd time, clock will show
press time set once
enter time
press am/pm button (below time set)
press time set for 3 seconds
press CE/E red button to return to calculation mode

thats it

I don't think the P23-DH has a calendar/clock mode. I have found the instructions for setting date and time for the P23-DH V. If your calculator does not have [Calendar/Clock], [Time Set], and [AM/PM] keys, you cannot set the date and time.

To set date:
1. Press the [Calendar/Clock] key once
2. Press and hold the [Time Set] key for three seconds
3. Enter the date in MMDDYYYY format
4. Press the [Time Set] key
5. Press the [C/CE] key

To set time:
1. Press the [Calendar/Clock] key twice
2. Press and hold the [Time Set] key for three seconds
3. Enter the date in HHMM format, press [AM/PM] key if necessary
4. Press the [Time Set] key
5. Press the [C/CE] key

Press the Time/Date Button.

Press and hold the = button for three seconds until the first number on the left starts blinking.

Input data.

Press and hold the = button for a second.

SAME OPERATION FOR DATE AND TIME.

Only the best regards,
Roman V. Martynyuk

P.S.
I had to call canon for this solution, so enjoy my brothers and sisters, aunts and uncles!

How to change the roller ribbon on my Canon P100-dh calculator?

I played around with mine and found the keys that you change the time and date with by looking over the top of the keyboard. On my model there is a time and date key that has a little calendar and clock actually on the key. That key allows you to switch between date and calendar. After you click on that button you will either see a date or time. To change those numbers use the following keys: The equal (=) key will change date and time by holding the key down till the numbers on the display start to flash. Once they start to flash use the number keys to make your changes. The multiplication (X) key you can use to change am and pm. If you want military time use the division key. If you are changing the date there is an additional key that lets you change the format. What this means is the sequence on the display by the way you view the month, date and year. You can change it so year shows first then month and date or interchange day and month. Once I found those keys it was easy.