Keeping time with coin battery

I was a bit puzzled and got the solution.

Just a remember that you have to change the hardware clock to keep the time with a coin battery. When you only set the software clock, it doesn't keep the time with the battery (makes sense). You have to sync the clocks. First, I set the system time and date with date +%Y%m%d%H%M -s "201401102348" and then sync the clocks with that command (I use UTC); hwclock --systohc --utc

It works !