Specifies the method and format used to set the system time.
'manual': Operator must configures the system time
parameters manually in the GMT zone.
'sntpUdp': Look for time servers in the
systemTimeServerTable in order to synchronize
the device system time using SNTP.
'tp': Look for time servers in the systemTimeServerTable
in order to synchronize the device system time using
the Time Protocol.