As the time of posting was 5 seconds early this seems to indicate that it took about 4 seconds from when you posted it until when it was actually done. So you might need to post at 11:59:56 to get an exact midnight posting. More investigations may be required to confirm.
I posted this right on the clock
Not quite
the clock on my pc was 12.00
I now have to investigate this
investigation done, my clock is 8.3 seconds ahead!!
my clock is now synchronised
I had time.is up ready to beat you
As the time of posting was 5 seconds early this seems to indicate that it took about 4 seconds from when you posted it until when it was actually done. So you might need to post at 11:59:56 to get an exact midnight posting. More investigations may be required to confirm.