For KX-T7730 how do you set /change date/time and date ? Also day like mon tues etc ?

Press Program
0
you will see a display (January 19, 2011 - display 110119)
enter your date (don't press any other buttons, the phone will do in sequence)
YYMMDD
enter day of the week (1-Mon, 2-Tues, so on)
3
enter time (don't forget to enter 0 if like 9:30)
0930
enter AM or PM (0-AM, 1-PM)
0
then press store button
then press program button
you should see your date and time display

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and you
are done.

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and you
are done.

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and you
are done.

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and congratualations - you are done.

You have to change from extension 101. Once you are on extension 101 then you need to press program then 0. enter date backwards ie(081104) then day (1=mon 2=tues 3=wed 4=thur 5=fri ect.) then enter time ie(0300 for 3:00) then 0 for am or 1 for pm. so it would go like this
Press program then 0
Enter (example for Tues. Nov. 11,2008 3:00 pm) would be
081104 2 0300 1
then press store then program again and it's set.

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system. From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle press PROGRAM * # followed by the system password ( default is 1234). Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ). Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered. Press PROGRAM to exit program mode and you are done.

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and you
are done.

Basically, there are 2 ways of programming the date
and time - the short way and the long way.
If you are using the KX-T7730 phone on a Panasonic
KX-Txx 308/824 system:

SHORT WAY:
From the Switcboard / Main telephone
( ext 101, 10 or 9 ) with the handset on the
cradle/hook:
1. Press PROGRAM 0
2. Enter Date and Time
( The format is: yymmdd,
1 to 7 1=Monday 2=Tuesday etc, hh:mm,
0 or 1 0=AM 1=PM ) see example
3. Press AUTO DIAL / STORE to save your changes
4. Press PROGRAM to exit program mode

EXAMPLE:
If the date and time is 3 February 2010 Tuesday 2:15 pm you will enter as follows:
100203 2 02:15 1

LONG WAY:
From the Switcboard / Main telephone ( ext 101, 10 or 9 ) with the handset on the cradle/hook:
1. Press PROGRAM * # followed by the system
password ( default is 1234).
2. Now press 000 and then SP-PHONE.
Enter the year.
3. Scroll to the month with the right scroll key
(located at the right bottom corner of the phone).
To change the month use the AUTO ANS / MUTE
button.
4. Now scroll right again and change the date and
day.
To change the day, again use AUTO ANS / MUTE
5. Scroll right again and the time will appear.
Set the time.
To change am/pm scroll to it, and again,
use the AUTO ANS / MUTE button.
6. Press PROGRAM to exit program mode and you
are done.

You will need to enter programming mode. Here are the directions.
You must be on the main phone on jack 01 to set time. You can determine if your phone is jack 01 by setting the switch on the end of a display phone to PROGRAM and then pushing the number 6 on the dial pad. The phone will read the jack and extension number. When you have determined the jack 01 phone, do the following.

1. Set switch on end of phone to "PROGRAM" (or push PROGRAM key if you have one)
2. Dial "0"
3. Enter year (last 2 digits)
4. Enter month (01-12)
5. Enter day (01-31)
6. Enter day of week (Sun 0, Mon 1, Tue 2, Wed 3, Thu 4, Fri 5, Sat 6.)
7. Enter Hour (01-12)
8. Enter Minute (00-59)
9. Press 0 for AM 1 for PM
10. Press "AUTO DIAL/STORE" key
11. Return phone switch to "SET" (or push PROGRAM key if you have one)

http://telephones.att.com/telephones_ui/support/dsp_manual.cfm?manualID=339


Here's the official AT & T link for your manual.