Nikon D6 Reference Manual page 1080

D
The ! Icon
A flashing ! icon indicates that the camera clock has been reset. The date
and time recorded with new photographs will not be correct; use the
[Time zone and date] > [Date and time] option in the setup menu to set
the clock to the correct time and date.
A
Using the i Menu
To access the i menu, press the i button or tap
the guide in the information display. Press the
i button again or press the R button to return
to the information display when settings are
complete.
1028 Camera Displays