KPanasonic X-TAW848
  1. Use phone with intercom number 101. It will change the time for all phones.
  2. Press PROGRAM (or PAUSE, if you don't have a PROGRAM button.) 
  3. Dial programming access code (probably *#1234)
  4. Press NEXT (SP-PHONE, if you are not using the programming template). 
  5. You'll see "Date & Time Set" on your phone's display
  6. Press STORE
  7. Press NEXT to see hours and minutes.
  8. Use your keypad to change the hour
  9. Press STORE.
  10. Press HOLD. 
  11. Press PROGRAM