AT&T Lucent Partner Systems (ACS, Endeavor, Partner Plus, Partner II)
All programming is done at ext. 10 or 11

1) Press feature key, then 00 (enters programming mode)
2) Press left intercom button twice
3) #103 (code to change system time)
4) Enter correct time (military time)
5) Press feature key, then 00 (exit programming)