Canon EOS 5D Mark III Instruction Manual (en)

 Setting the Time Code
Time code
You can append the time code to a movie that was output from 
HDMI (p.246).
[On]: Time code is appended to the HDMI output image.
[Off]: Time code is not appended to the HDMI output image.
Recording command
When you record a movie that is output from HDMI to an external 
recording device, you can synchronize the camera’s movie shooting 
start/stop with the external recording device’s recording operation.
[On]: Synchronize external recording device’s recording start/stop 
with camera’s movie shooting start/stop.
[Off]: Control external device’s recording start/stop from external 
recording device.
If the movie-recording quality’s frame rate (p.233) and HDMI output frame 
rate are set manually to NTSC and PAL frame rates in a combination that 
does not function properly, the time code will not be appended to the HDMI 
output image.