If it's the same as my XA 3000 then:-
1. Press the tick button on the handset twice.
TAM MENU should flash on the display.
2. Press the 0 button.
The prompt will announce "To set day and time press * (star button)".
3.Press the * button.
The prompt will announce "Please enter the new day and time after the tone".
After the tone enter day as follows 1= Sunday 2= Monday etc. followed by the time on a 24 hour clock eg
5 1415 is Thurs 2.15 pm.
After hearing confimation press the CROSS button on the handset twice.
Hope this helps.