If you set up your base station or your Time Capsule to log status information to the Mac OS X system log (or syslog host), or you’re using timed user access on a network that supports it, you need to set the base station or your Time Capsule to set the date and time automatically. This ensures that the logs are accurate, and users can access the network at the correct times.
To set the time automatically, you need to have access to a network time server (NTS) either on your network or on the Internet.
Open AirPort Utility, located in the Utilities folder in the Applications folder on a computer using Mac OS X, and in Start > All Programs > AirPort on a Windows computer.
Select your device, and then click Manual Setup. Enter the password if necessary.
Click AirPort in the toolbar, and then click Base Station or Time Capsule, depending on what you’re setting up.
Select the "Set time automatically" checkbox, and then choose a time server from the pop-up menu.
Choose your time zone from the Time Zone pop-up menu if your device supports it.