Date and time settings disabled My date and time has suddenly become  1 jam 2013

In date and time preferences the setting "set date and time automatically" is disabled by which I mean it's greyed out. It's ticked and set to 10.2.0.90

How can I reenable this setting to change the date?

MacBook Pro with Mavericks
Generally speaking you must be an administrator to change this setting. If you are using a non-admin account you can click on the lock at the bottom of the pref window and enter any admin credentials to enable the setting.