On the KX-T 1232 System you must first locate extension 101 for programming.  At extension 101 with the
handset hung up and SP-PHONE button off - set the memory switch (in the back of the phone) to  
"PROGRAM" then dial "0" - then enter the following as a complete string*

year (2-digits) month (2-digits) day (2-digits) day of week (
0=Sun    4=Thurs )   Enter hour (2-digits)
last 2 digits                   01 - 12                    01 - 31                              1=Mon   5=Fri                        01 - 12
                                                                          2=Tues  6=Sat
                                                                          3=Wed

Minutes (2-digits)  Dial 0 for AM                Press Memory Key
(00-59              Dial 1 for PM

Then remember to set the memory switch back to Set.  All display sets should now show the new time.

*e.g. 040316201431 would be the setting for March 16, 2004 - Tuesday - 1:43 P.M.