Recently I have encountered 2 cases where the wrong system time caused serious problems regarding the windows and antivirus updates.

Both systems are old and the mobo battery has runned out, so every time they are unplugged or there is a power failure the system time is lost.

In the first case, this happened to a windows vista laptop. This had as a result for the antivirus - microsoft security essentials (MSE) - definitions to be several months old, and the computer to catch the infamous police virus.

Virus removal was easy but the question why a protected computer cathed a virus arised.

The answer is that the wrong time made MSE to think that it has already the latest virus definitions installed.

In the second case, an old P4 that I have just installed windows 7 couldn’t perform windows updates because of the wrong time. I have spent quite some time reviewing the network configuration before I notice that.

In most linux systems, the update mechanism checks only the versions of the local packages, so the local time wouldn’t affect that.

However, there are other functions like authentication and stuff like that, that require the correct local time.

The solution is definitely to buy a new battery for your motherboard!

One could say that synchronising the clock via ntp would work bur unfortunately ntp syncing isn’t working for large differences between the local and the remote clock. Syncing is going to work only for ~4 minute differences.

Every computer and exceptionally windows should have correct local time, especially if they are communicating with other systems. Doing otherwise could cause communication failures and security threats.