(User’s Manual – D300S page 302; D300 page 316)
Time zone and date (D300S) or World time (D300) allows you to configure the Time zone, Date and time, Date format, and Daylight saving time for your camera.
If you haven’t set the time and date you’ll see the word CLOCK flashing on the Control panel. In addition to the main Li-ion battery pack, the camera has a built-in clock battery that is not user-replaceable. The built-in battery charges itself from the main camera battery pack. CLOCK blinking in the Control panel can also mean that the internal battery has become exhausted and the clock has been reset.
It takes about two days of having a charged battery in the camera to fully charge the separate built-in clock battery. ...