During regular check of my Hyper-V hosts (Windows servers 2008 (R2)) I have seen that some of them have time out of sync even if all of them have configured external NTP source (I am using pool.ntp.org – in my case si.pool.ntp.org (Slovenian pool))…

But by default Windows is making NTP query and correction every 7 days (604800 seconds :))…

Well as NTP query is from network prospective small / light I have decided to make this check and sync once per hour… (3600 seconds)…

Well where do we set up this?

The key that you need to change is located in:

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServices
W32TimeTimeProvidersNtpClientSpecialPollInterval

Change from 604800 to 3600 (1 hour for example)… And restart Windows Time service

You can check snapshots on:
https://skydrive.live.com/?cid=38C674F31C0CB95C&id=38C674F31C0CB95C%212390#cid=38C674F31C0CB95C&id=38C674F31C0CB95C%212391