What consequences / implications can arise from a wrong system clock?

What issues can you think of that may arise from a wrong system clock setting ?

Primarily interested in potential problems affecting servers and Linux or UNIX-like systems in particular.

And how severe are these consequences, depending on how much the system time is off ? For example, 5 minutes, 30 minutes, 1 hour, 1 day.

Solution 1:

Well for one your timestamps on all your logs will be off and out of sync with other servers making it very hard to figure out when things happened. Also, time synchronization is relied upon for some security protocols (kerberos for example).

So what I'm saying is, most things will continue working normally, some protocols or applications relying on accurate time may break, and you as the admin will generally have some headaches for it.

Configure NTP against a provider like pool.ntp.org or NIST and call it a day.

Solution 2:

Here's just a few:

• MySQL replication
• Database queries using now() for current date/time
• rsync backup scripts
• any other inter-server communication

NTP is the best way to keep your time correct.