Unable to perform initial settings

you may have to enitial the time and date wen you set it

NVRAM initialization
CAUTION NVRAM initialization will erase all network settings. Before performing NVRAM
initialization, print a Network Configuration page, which contains network-setting information.
NVRAM initialization performs the following actions:
? Resets all customer-accessible menu settings via control panel and software back to the factory
default settings
? Resets the language to the value set at the factory
? Resets the default media size to cold reset media size
? Resets the symbol set to PC-8
NOTE The following steps reset the same NVRAM locations that are reset using the
Restore Defaults option in the control panel Service menu. The following process should be
used if the MFP does not come to a Ready state and an NVRAM initialization is desired.
Use the following procedure to perform an NVRAM initialization.
1. Turn off the printer.
2. Press and hold the Right arrow and Cancel buttons simultaneously.
3. Turn on the printer.
4. When you see the message Permanent storage init, release the Right arrow and Cancel buttons.
When the NVRAM init is complete, the printer returns to the Ready state.

Cold reset
A cold reset changes most system parameters in NVRAM to the factory defaults. However, unlike NVRAM inititialization, a cold reset does not reset the page count, the paper tray sizes, language, or formatter number.
Note If an HP Jetdirect card is installed, remove it before performing a cold reset. Otherwise, the procedure will also reset all the HP Jetdirect settings as well as the printer settings.
To perform a cold reset
1 Turn the printer off.
2 Press and hold down the GO button.
3 Turn the printer on, and continue to hold the GO button for at least 5 seconds, but not longer than 15 seconds. During this process, the Attention LED will turn on.
4 Release the GO button.
Note If both the Attention and the Ready LEDs turn on before you release the GO button, you must start the procedure again with step 1.
5 The printer's LEDs will begin cycling. The cold-reset process will
run until completion, and the printer will return to the ready state.

If not work, tris this

NVRAM initialization

CAUTION Only perform the following procedure if absolutely necessary.
Performing an NVRAM initialization resets some parameters that cannot be restored later.
NVRAM initialization sets all default variables stored in NVRAM back to factory default values or to a default ROM value, depending on the variable. It also performs a system reset.

NVRAM initialization resets the following:

• all menu settings to factory default values

• factory settings such as formatter number, page counts, and factory paper settings
  

To perform NVRAM initialization
1 Turn the printer off.
2 Press and hold down the GO button.
3 Turn the printer on, and continue to hold the GO button for at least 20 seconds. During this process, the GO button, Attention, and Ready LEDs will each turn on.
4 Release the GO button.
5 The printer LEDs will begin cycling. The NVRAM-unit process will run until the printer is in the ready state.

Press SRC/OFF and hold until the unit turns off. Then press the Multi Control (M.C.) and hold until function name appears in the display. Turn M.C. select the initial setting. After selecting, perform the following procedures to set the initial setting. 1. Press M.C. to display the setting mode. 2. Press M.C. to select the segment of the clock display you want to set. Hour - Minute. 3. Turn M.C to adjust the clock.

See instructions below:
----------------------
Initial Settings
Adjusting initial settings
Using the initial settings, you can customize
various system settings to achieve optimal performance
from this unit.

1 Press SOURCE and hold until the unit
turns off.
2 Press FUNCTION and hold until function
name appears in the display.
3 Press FUNCTION repeatedly to switch
between the following settings:
CALENDAR (date and clock)—
WARNING TONE (warning tone)—AUX1 (auxiliary
input1)—AUX2 (auxiliary input2)—
DIMMER (dimmer)—S/W CONTROL (rear
output and subwoofer controller)—
DEMONSTRATION (feature demo)—
EVER-SCROLL (ever scroll)
Use the following instructions to operate each
particular setting.
# To cancel initial settings, press BAND.
# You can also cancel initial settings by holding
down FUNCTION until the unit turns off.

Setting the date and clock
Use these instructions to set the clock.
1 Press FUNCTION to select clock.
2 Press c or d to select the segment you
wish to set.
Day—Month—Year—Hour—Minute
As you select segments of the clock display
the segment selected will blink.

3 Press a or b to set the date and clock.
Pressing a will increase the value of the selected
segment. Pressing b will decrease the
value of the selected segment.
-----------------------
http://www.pioneerelectronics.com/pio/pe/images/portal/cit_11221/415128381DEHP4900IBOperationManual0216.pdf

you must first disable Autoupdate (turn it off) - go to settings>scroll to Initial Setup, (select this)>Time & Date (select this)>Autoupdate (set to OFF)>after you do this option will appear to change time to 12/24 hour....

try this:
Adjusting initial settings
Using the initial settings, you can customize
various system settings to achieve optimal performance
from this unit.
1 Press SOURCE and hold until the unit
turns off.
2 Press SOURCE and hold until function
name appears in the display.
3 Press FUNCTION to select one of the initial
settings.
Press FUNCTION repeatedly to switch between
the following settings:
Clock—AUX (auxiliary input)
Use the following instructions to operate each
particular setting.
# To cancel initial settings, press BAND.
# You can also cancel initial settings by holding
down SOURCE until the unit turns off.
Setting the clock
Use these instructions to set the clock.
1 Press FUNCTION to select clock.
2 Press c or d to select the segment of
the clock display you wish to set.
Pressing c or d will select one segment of the
clock display:
Hour—Minute
3 Press a or b to set the clock.
Turning the clock display on or off
You can turn the clock display on or off.
! Even when the sources are off, the clock
display appears on the display.
% Press CLOCK to turn the clock display
on or off.
Each press of CLOCK turns the clock display
on or off.

It's on page 12 of the manual. Here you go:
http://www.pioneerelectronics.com/pio/pe/images/portal/cit_11221/372010482DEH1900MPOperationManual1030.pdf

Adjusting initial settings
Using the initial settings, you can customize
various system settings to achieve optimal performance
from this unit.
1 Press SOURCE and hold until the unit
turns off.
2 Press SOURCE and hold until function
name appears in the display.
3 Press FUNCTION to select one of the initial
settings.
Press FUNCTION repeatedly to switch between
the following settings:
Clock—AUX (auxiliary input)
Use the following instructions to operate each
particular setting.
# To cancel initial settings, press BAND.
# You can also cancel initial settings by holding
down SOURCE until the unit turns off.
Setting the clock
Use these instructions to set the clock.
1 Press FUNCTION to select clock.
2 Press c or d to select the segment of
the clock display you wish to set.
Pressing c or d will select one segment of the
clock display:
Hour—Minute
3 Press a or b to set the clock.
Turning the clock display on or off
You can turn the clock display on or off.
! Even when the sources are off, the clock
display appears on the display.
% Press CLOCK to turn the clock display
on or off.
Each press of CLOCK turns the clock display
on or off.
Operating this unit
12 En

Go to settings
--> Initial Setup
--> Time and date
--> Auto update off

Then you will find the time and date.

go to date use right soft key and change the date and similarly for the time.

Settings
Initial Setup
Time and date

• Turn AutoUpdate Off

select and make the change