Nikon 1 J5 Reference Manual page 53

A
The Camera Clock
The camera clock is less accurate than most watches and house-
hold clocks. Check the clock regularly against more accurate time
pieces and reset as necessary.
The camera clock is powered by an independent, rechargeable
power source, which is charged as necessary when the main bat-
tery is installed or the camera is powered by an optional power
connector and AC adapter (0 204). Three days of charging will
s
power the clock for about a month. If a message warning that the
clock is not set is displayed when the camera is turned on, the clock
battery is exhausted and the clock has been reset. Set the clock to
the correct time and date.
31