Using a NTP server with the Aastra 6731i in Africa is difficult since the phone has settings for the rest of the world except Africa - especially Namibia. Edit and add the following to the aastra.cfg file (bold red was added, bold blue is optional if Daylight Savings Time is to be used):
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# Time Server Settings
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time server disabled:0 #server enabled(0), server disabled(1)
dst config: 0 #daylight savings, OFF(0), 30 min summertime(1), 1h summertime(2), automatic(3)(default)
time server1:172.16.104.72
time server2:172.16.104.73
#time server2: # least one time server IP address or
#time server3: # qualified domain name
#Time and Date Settings
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time zone name:Custom #Required setting if time-server is enabled
time format:1 #12hours(0), 24hours(1)
date format:2 #YYYY-MM-DD(2)
time zone minutes: -120 #For GMT +2 = -120, for GMT +1 = -60
#dst minutes: 60 #Amount of minutes to add for DST
#dst [start/end] relative date: 1 #1 = relative, 0 = absolute
#dst start month: 4 #1 = January
#dst end month: 8 #12 = December
#dst start week: 1 #First week of the month = 1
#dst end week: 1
#dst start day: 7 # 1 = Monday
#dst end day: 7
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