I spend some time to lower the overall power consumption in order the clock could run on batteries. I'm sure there is still rooms for improvements. The CPU is on sleep, and only the second 32.768Khz oscillator is running for RTC and LCD driving. All unused peripherals are off. It wakes up every seconds to update. Right now everything consume roughly 200uA.

I used directly 3 NiMH AA batteries, no regulator. That's give voltage between 4V amd 3.3V. Let see if it last at least few month.

I made a quick frame :

And now, no relief ! Could no say "Oh god, I didn't see the time passing while I'm playing...."