People live in North America know there are 2 time changes every year. Even there is NTP to help all devices to sync time properly, but sometime devices are not that smart to know when to adjust.
Here below is an example of configure NTP on cisco device, which located in Atlantic Timezone:
Router(config)# clock timezone AST -4
Router(config)# clock summer-time ADT recurring 3 Sunday March 2:00 2 Sunday November 2:00 60
Router(config)# ntp server pool.ntp.org
Here below is how to use the windows server as the ntp mast for gears inside network:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type ->Set value to NTP.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags ->Set the value to 5 for reliable time source
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPClient\SpecialPollInterval ->Set this to the preiod in seconds that the Windows 2003 machine should poll the NTP server. A recommended value is 900 seconds which equates to every 15 minutes.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPServer\Enabled ->Change this value to 1.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer ->Provide a list of IP address or DNS names, seperated by a space, of NTP server that the Windows 2003/2008 machine can synchronise to.