It’s officially September now (in some parts of the world), and that means we’ve been watching the Christmas decorations go up on the floor of Costco, Walmart and Target for the last few weeks. As a small test of reality, [Eric] decided to build an electronic advent calendar that counts down the days until Christmas. As a simple build using parts lying around on the bench, [Eric] did a pretty good job at deferring his kid’s questions of, “How long until Christmas?” to a machine.

The build is fairly bare-bones, using only an Arduino Pro Mini, RTC and LCD display. For the real-time clock, [Eric] used the ever popular DS3231 RTC. The software reads the time from the clock and calculates the number of seconds between the present time and the hard-coded target date.

Everything is powered by a 9 Volt battery that wouldn’t last the remaining 115 days until Christmas. There is a power switch and the RTC has a battery backup, so the build will probably suffice for all but the most fanatical child.