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You can manually configure the NTP settings on your Polycom or Aastra phone if you follow these directions:
Aastra
Find the IP Address of your phone
Open your web browser and navigate to that IP address (type it into the URL field)
Login with username admin and password 22222
Click on Network Settings
Set Time Server 1 to http://pool.ntp.org
Click Save Settings
Click on Reset
Click on Restart Phone
Polycom
Find the IP Address of your phone
Open your web browser and navigate to that IP address (type it into the URL field)
Login with username Polycom and password 456
Click on General
Set the SNTP Server to http://pool.ntp.org
Click Submit
As long as the router in your remote location allows the phone to communicate with http://pool.ntp.org , the phone should correctly synchronize with the local time.