You can SSH into the AMP and use the date command to change the system time and date. Check the current date, time setting on the server with the date command alone:
Change the date, time as follows:
# date MMDDhhmmCCYY
For example, to set the clock to November 12, 1975 3:42PM:
# date 111215421975
Please be aware that if the date was set incorrectly in the future, it will affect the RRD data (http://kb.airwave.com/?sid=50140000000ZyO5). If the date was set in the past, then things should work as normal, but you will see a gap in the graphing data representing the change in epoch time.