Amazon EC2 virtual servers’ internal clock is synchronized with that of their host server. But some host servers seems to be off-date: I’m working on a four-server cluster (will grow to eight when we go into production) and while three of them were perfectly synchronized, the fourth one lagged behind a couple of minutes.
By default you can’t adjust the date with either date nor ntp, the commands execute but do nothing. In order to decouple the VM’s clock from the host’s one and being able to set the time on your system you need to run the following command:
Bear in mind that, as pointed out here, after decoupling your clock from the host’s you can’t go back, you’ll be on your own forever.