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https://confluence.cornell.edu/x/GDeJFg

Virtual Machines

What are the recommended settings for synchronizing the system clock?

Images from the Azure Marketplace should include default configurations for system clock management.  These range from using an emulated real-time-clock within the guest or reaching out to public network time servers around the world.

 In cases where you have configured restrictive Network Security Groups (NSG) that limit out-bound traffic, you should confirm that outbound probes to NTP servers are permitted.  Typically, this traffic operates on UDP port 123.  No special in-bound are required, since NSGs at Azure are stateful.

Additional details may be found in Microsoft's published guidelines for clock synchronization when running Linux platforms or Windows platforms in Azure.