ntp and ntpdate are UNIX shell commands exposed in Director. Following is a summary of the differences between these commands:
ntpdate synchronizes the clock with an NTP server one time whereas ntp starts and stops the Network Time Protocol Daemon (ntpd) service, and the ntpd keeps Director’s clock in synchronization constantly.
ntp has an algorithm that calculates and fixes the drift in your server's clock, whereas ntpdate does not keep any state to perform this service for you so will not provide the same kind of accuracy.
If Director’s clock is inaccurate by several hours, and you are using ntp, you should restart Director. On restart, ntp uses ntpdate to reset the system clock.
IMPORTANT: Do not use ntpdate if the ntpd is running. Doing so can result in unpredictable performance. Instead, use the reload command to restart Director.
For more information, see one of the following articles. Note that the Director ntp and ntpdate commands do not support optional command-line switches discussed in these articles. Director’s commands support only the parameters discussed in this book.